A systematic review and meta-analysis of appointment reminders for enhancing hospital attendance

Introduction

Missed hospital appointments, often referred to as non-attendance, no-shows or failure to attend, are a challenge for healthcare systems worldwide (1). Patient non-attendance reduces the efficiency of healthcare delivery, leading to underutilised resources, increased waiting times, and potentially poorer patient outcomes due to care delays. Addressing this issue is crucial not only from an operational perspective, but also to improve patient satisfaction and overall healthcare quality.

Various initiatives have been proposed or implemented to increase attendance rates and decrease non-attendance, such as patient incentives or rewards for attending their scheduled appointments (2), imposing fines or penalties on patients who miss their appointments (3), and allowing patients greater flexibility by providing more options when scheduling appointments may also improve attendance (3). Transportation and culture have been highlighted as potential barriers to attendance in hospitals. Chaiyachati et al. [2018] suggested that providing transportation could facilitate attendance, while Gatrad [2000] emphasized the importance of considering cultural factors, such as religious holidays, when scheduling appointments (4,5). Among the proposed strategies to improve attendance, sending appointment reminders to patients is worthwhile—whether via postal mail, phone calls, or short messaging service (SMS) messages, with the latter receiving international attention, as it is the most widely used, implemented and successful (6-9). Reminders are easy to implement and potentially effective methods to prompt patients to attend scheduled appointments, thus reducing the likelihood of missed appointments due to forgetfulness or miscommunication. Despite their widespread usage, uncertainty remains as to which types of reminders improve attendance rates more than others.

From a hospital management perspective, economic evidence is critical for resource allocation. Missed appointments consume fixed clinic capacity, generate rebooking and administrative work, and may displace care to more expensive settings. Accordingly, assessing the cost-effectiveness of reminder strategies beyond reporting basic delivery costs helps determine whether a given approach yields additional attended appointments at an acceptable incremental cost and is scalable within constrained budgets.

Although previously conducted systematic reviews have examined the effectiveness of various types of appointment reminders in diverse healthcare settings, including primary care settings, out-of-hospital outpatient clinics, and specialized care facilities, none was found that specifically focused on evaluating reminder interventions aimed at reducing non-attendance at hospital out-patient departments only, where appointment adherence is often essential for timely diagnostics and treatment (10,11).

The rationale for this review was to examine randomized controlled trials (RCTs) that assessed the effectiveness of appointment reminders in improving attendance rates specifically in hospital out-patient settings among adults. Compared to community or primary care clinics, hospital-based outpatient departments often serve patients with more complex conditions requiring timely diagnostics or interventions. Missed appointments in these settings may lead to delays in specialist care or prolonged disease progression. Therefore, by focusing exclusively on hospital-based out-patient studies, this review provides detail on the types of interventions used and their effectiveness in these resource intensive settings. The primary review objective was to identify the types of reminder interventions in use and evaluate their effectiveness in improving attendance rates at outpatient hospital appointments. A secondary objective was to report on cost associated with intervention reminders, if reported by any of the studies. We present this article in accordance with the PRISMA reporting checklist (available at https://jhmhp.amegroups.com/article/view/10.21037/jhmhp-25-51/rc).

Methods

Protocol development and registration

The protocol for this review was registered with the International Prospective Register of Systematic Reviews (PROSPERO) under protocol No. CRD42024497967.

Preliminary research and concept validation

The search uncovered systematic reviews and meta-analyses assessing the effectiveness of reminders in various healthcare environments.

Design

This systematic review and meta-analysis were conducted using the principles of the Cochrane guidelines for systematic reviews of interventions.

Inclusion criteria

Studies were included if they were randomised and quasi-RCTs reporting on hospital attendance rates. The target population consisted of adult patients, aged 18 years or older, with scheduled outpatient appointments in hospital settings. Studies from any geographic region or healthcare system were included to offer a global perspective on the use of reminder systems. Included studies were limited to those published in the English language.

Exclusion criteria

Non-parallel group RCTs, such as cluster RCTs, crossover trials, observational studies, cohort studies, and case-control studies, were excluded. Interventions that were implemented in settings outside of hospitals, such as primary care clinics, those that did not report findings for adults separate to those <18 years of age and studies not published in English were also excluded.

Outcome measures

The primary outcome measure was hospital appointment attendance rate, which had to be reported explicitly as a key variable for a study to be included. As a secondary outcome, and where it was available, a narrative summary of the costs associated with the implementation of reminder interventions was included as an outcome measure.

Search strategy

The literature search was conducted between August 2023 and February 2024. No date restrictions were applied. All records available in each database up to October 2023 were considered during the search. A preliminary scoping search using the keyword “hospital appointment reminders” was conducted to development of the search strategy for this review (12). The researcher collaborated with a subject librarian to design the search strategy. The search terms included “reminder systems”, “appointments and schedules”, and “non-attendance”, as well as relevant Medical Subject Headings (MeSH) terms obtained from the National Center for Biotechnology Information (NCBI) MeSH database. The search was conducted in Medical Literature Analysis and Retrieval System Online (MEDLINE), Cumulative Index to Nursing and Allied Health Literature (CINAHL), Web of Science, and Embase databases. No publication date restrictions were applied to the search. The search was confined to papers published in the English-language and electronic database peer-reviewed studies only, due to resource limitations. The full search strategy for all databases is provided in Appendix 1.

Study selection process

The study selection process was performed against the inclusion/exclusion criteria in two stages: first, screening based on title and abstract, followed by a full-text eligibility review. Rayyan software was utilized to manage the screening process as it offers ease of navigation and automatically detects duplicate entries (12). To minimize bias, two independent reviewers screened the studies (13,14). Two authors (M.A.T. and M.C.) reviewed title and abstract followed by full-text screening. Discrepancies were resolved through discussion, and when consensus could not be reached, M.M. was consulted. This process was documented in Rayyan.

Quality assessment and data extraction

The methodological quality of the selected studies was assessed using the Cochrane Collaboration’s risk-of-bias tool (RoB 2), which evaluates studies in five key domains: randomization, deviation from the intended intervention, missing outcome data, participant and personnel blinding, and selective outcome reporting. Each study was categorized as having low, high, or some concern of bias, based on the collective assessment across their five domains.

Data extraction was performed with a tailored extraction form developed from Cochrane Collaboration templates. The first author extracted the relevant data, which M.M. and M.C. then verified for accuracy. The extracted information included key study characteristics, such as the author, publication year, study location, sample size, design, and participant demographics (e.g., age, gender, education level, marital status, and distance from the hospital). Details about the type of intervention (e.g., SMS message, phone call, or postal reminders), timing, frequency, and nature of the appointment (first appointment, follow-up, or investigation) were also recorded. Attendance rates, along with event and total numbers for both reminder and non-reminder groups, were recorded, as well as intervention costs where available.

Statistical analysis

The statistical analysis was conducted using RevMan Web, The Cochrane Collaboration, available at https://revman.cochrane.org/. The primary outcome, hospital appointment attendance rate, was analysed by calculating risk ratios (RRs) using Mantel-Haenszel method with a random-effects model. This method was selected to pool dichotomous outcomes while accounting for both within- and between-study variability, recognizing potential clinical and methodological heterogeneity across studies. RRs with 95% confidence intervals (CIs) were calculated to estimate the relative effect of the intervention. Studies were weighted according to their sample sizes and forest plots were generated to visually summarize the findings. Heterogeneity was assessed visually and with I-squared (I²) statistics, with values above 50% indicating significant heterogeneity (15). A subgroup analysis was conducted to compare the effectiveness of different reminder methods, such as SMS messages and phone calls. Sensitivity analyses were performed to examine individual studies’ impact on the overall results and to ensure robustness. Studies in which patients contributed data from multiple outpatient appointments were not included in the meta-analysis, as repeated attendance outcomes violate the assumption of independent observations required for pooled effect estimation. These studies were instead synthesized narratively.

To detect potential publication bias, Egger’s test was applied with MedCalc software. This statistical test evaluates the symmetry of the funnel plot by regressing the effect sizes against their standard errors (SEs) (15). A P<0.05 indicates the presence of significant publication bias (16).

Results

Search outcomes

The search of the MEDLINE, CINAHL, Web of Science, and Embase databases produced 1,799 records. Duplicates (n=918) were removed leaving, 881 unique records, of which 855 were excluded at title and abstract screening. The remaining 26 studies were screened at full-text level resulting in the exclusion of 14 studies for reasons including a focus on paediatric populations (2 studies), a lack of full-text availability (2 studies) and not hospital settings (9 studies). Although 13 studies fulfilled the inclusion criteria only 12 were included in the analysis as one study had missing data and attempts to contact the authors were unsuccessful. Although 12 were included, two were synthesized narratively rather than included in the meta-analysis because they reported attendance across multiple appointments per patient. The remaining studies evaluated attendance at a single outpatient appointment per patient and were included in the quantitative synthesis. The PRISMA flowchart in Figure 1 details the study selection process.

Figure 1 Preferred Reporting Items for Systematic Reviews and Meta-Analyses flowchart. CINAHL, Cumulative Index to Nursing and Allied Health Literature; MEDLINE, Medical Literature Analysis and Retrieval System Online.

Characteristics of selected studies

The 12 included studies spanned diverse hospital out-patient settings, and varied in terms of sample sizes, and countries of origin (Table 1). In the UK, two studies were conducted in specialist hospital departments-one in the respiratory outpatient clinic in London and the other in the orthodontic out-patient unit at the University Dental Hospital in Manchester (6,17). One study from South Korea was based in the neurology out-patient department of a university tertiary care hospital (18). In Spain, the selected studies took place in the dermatology and pneumology outpatient departments of Hospital Municipal de Badalona (8). Two studies from the USA also contributed to the review, one conducted with the Internal Medicine Associates of Massachusetts General Hospital in Boston and the other at a hospital in the Bronx, New York (19,20). A study in Malaysia was conducted in the psychiatry and mental health out-patient departments of Hospital Melaka, while in Saudi Arabia, studies spanned the general medicine, neurology, and obstetrics and gynaecology out-patient clinics at King Fahad Teaching Hospital (21,22). In Australia, two studies were conducted at the Royal Melbourne Hospital in the physical therapy outpatient department and the emergency department (23,24). In addition, a multi-site study which included five hospitals located in low-income regions of Guangdong, China, provided insight into reminder results among people in diverse socioeconomic contexts (25). Additionally, one quasi-randomized study from Hong Kong evaluated SMS reminders for outpatient colonoscopy across three public clinics, with procedures performed at Alice Ho Miu Ling Nethersole Hospital (26).

The sample sizes in the studies varied, reflecting differences in scope and research settings and ranged from 183 to 2,247 (19,22). A large quasi-randomized colonoscopy study from Hong Kong (n=2,225) also falls at the upper end of this range. The demographic information provided in the selected studies offered insights into how factors, including gender, age, education level, marital status, and distance from the hospital, might influence the effectiveness of reminder interventions to improve appointment attendance. However, the focus on these characteristics varied across studies. Some studies consistently reported the sample’s gender distribution, with most showing broadly equal numbers of male and female participants. For example, Roberts et al. [2007] included 209 men and 295 women, while Shah et al. [2016] had 1,081 men and 1,166 women (17,19). Similarly, Lam et al. [2021] reported broadly balanced sex distributions between arms (men 49.5% in the SMS arm vs. 48.6% in control; women 50.5% vs. 51.4%), consistent with other included studies. Age was generally reported as mean values with standard deviations (18,24). The reporting of participants’ education levels was less consistent with only two studies reporting its association with attendance rate (21,24). Low et al. [2021] reported that individuals with higher education levels were more likely to respond positively to reminders, whereas Chen et al. [2018] reported no significant association between education levels and attendance rates (25). Only two studies explored the influence of marital status, in which Low et al. [2021] found no significant association while Valero-Bover et al. [2022] noted that marital status was significantly associated with attendance rates in the pneumology department, although not in the dermatology department (8,22). Two studies highlighted the impact of patients’ distance from the hospital on attendance and found that travel distance contributed to whether patients attended their appointments (8,18). In contrast, Low et al. [2021] found no such association (22).

Two studies, Low et al. [2021] and Shah et al. [2022], were excluded from the quantitative meta-analysis and are presented narratively because they assessed attendance across multiple outpatient appointments per patient, resulting in non-independent observations. In these studies, reminder interventions were delivered repeatedly over a series of scheduled appointments rather than being evaluated against a single index appointment. Both studies reported improved attendance following reminder implementation; however, the magnitude of effect varied across appointments and could not be expressed as a single comparable RR. Due to this methodological heterogeneity, pooling these data with single-appointment studies was not appropriate. These studies were therefore not suitable for pooling but were retained in the review and included in the risk-of-bias assessment to provide a complete evaluation of the available evidence.

Characteristics of the intervention

This current review analysed the impact of three investigated appointment reminder methods including telephone calls, SMS messages, and reminder letters on patient attendance rates. These methods were assessed by type, content customization, appointment details, frequency, and timing relative to the scheduled appointment. Telephone reminders were employed in six studies and were typically implemented for both new and follow-up appointments (8,17-20,23). Healthcare professionals or researchers often initiated these reminders, which usually involved a single call during working hours, either a week or three days before the scheduled appointment (17,19). In the study by Kwon et al. [2012], a neurology trainee personally contacted patients to confirm their attendance and provide appointment details one day before the scheduled visit (18).

Short message service (SMS) reminders were employed in five studies, which delivered brief, personalized messages containing specific appointment details and instructions (21,22,24-26). For example, Youssef et al. [2014] involved messages in Arabic, while Taylor et al. [2012] included instructions for physical therapy sessions (21,24). SMS message timing varied with some messages sent 48 hours before the appointment while others were dispatched up to one week before the scheduled date (8,21). One study by Chen et al. [2018] implemented multiple reminders (three reminders per patient) to further encourage adherence (25). A large quasi-randomized trial in Hong Kong by Lam et al., [2021] tested a single SMS sent 7–10 days before outpatient colonoscopy. The message (Chinese language) included the appointment date/time and bowel preparation instructions [low-residue diet; split-dose polyethylene glycol (PEG)]. All patients also received the standard printed appointment slip and verbal instructions at booking. Furthermore, one study explored the use of reminder letters, sending patients pre-addressed, stamped postcards to confirm new appointments (6). These were typically dispatched at least two weeks before the scheduled date. Only three studies reported intervention costs but neither provided information on the overall financial impact of missed appointments (17,25,26).

Of the selected studies, five were financially supported by hospitals and health-related organizations (17,19,20,24,25). Six other studies did not specify their funding sources (6,18,21-23,26). One study stated that it utilized no external funding (8).

Low et al. [2021] reported that some participants raised privacy concerns about receiving reminder text messages on their mobile devices, indicating that such interventions may pose confidentiality issues (22). Only two studies (Andreae et al. 2017; Lam et al. 2021) reported formally registering its trial protocol (on ClinicalTrials.gov) (20,26).

Risk of bias in the included studies

The quality of the included studies was assessed with the RoB 2 tool, focusing on randomization procedures, deviations from intended interventions, the handling of missing outcome data, outcome measurements, and the selective reporting of results. The results of the quality assessment are visually represented in Figure 2, where green (+) represents low risk, yellow (!) signifies some concern, and red (−) indicates the evaluation of a high risk of bias. Five studies employed appropriate randomization processes to ensure participants were appropriately allocated to intervention and control groups (6,20,21,23,24). These studies used reliable randomization techniques, such as computer-generated sequences or random number tables, that effectively minimized selection bias. However, five studies were unclear about their randomization methods, raising uncertainty about the potential for bias in participant allocation (6,8,17,19,22). Two studies showed a high risk of bias for the randomization process: Kwon et al. [2012] due to non-random allocation and inadequate documentation of this process (18), and Lam et al. [2021] because allocation was determined by even/odd calendar dates (quasi-randomization) (26).

Figure 2 Evaluation of bias risk in included studies utilizing the Cochrane Collaboration’s risk-of-bias tool.

In terms of intervention implementation, nine studies had a low risk of bias, indicating that the planned interventions were executed consistently (8,17,19-22,24-26). However, three studies provided insufficient information about whether the interventions were applied as intended, which could have introduced variability to the results (6,18,23).

All studies were low risk in terms of missing outcome data and outcome measurements, meaning they handled and measured the data uniformly across participants, minimizing the potential for measurement bias.

Four studies had a low risk of bias and eight were flagged for some concern in terms of selective reporting (18,21-23,26). indicating that further information would be needed to confirm that all relevant outcomes were fully reported. Of the selected studies, only Taylor et al. [2012] had a consistently low risk of bias across all domains (24). Kwon et al. [2012] and Lam et al. [2021] showed a high overall risk of bias, largely due to randomization (18,26). The remaining nine studies were classified as having some risk of bias (6,8,17,19-23,25).

Meta-analysis outcomes

Reminders vs. no reminders

The meta-analysis includes only studies reporting attendance outcomes for a single outpatient appointment per patient; studies by Low et al. [2021] and Shah et al. [2022] involving multiple appointments per patient were excluded. Of the 10 studies, four evaluated SMS messages, and five evaluated telephone reminders. The meta-analysis revealed that both SMS messages and telephone reminders had a positive effect on attendance rates. Using Mantel-Haenszel random-effects for dichotomous outcomes, the result revealed a pooled RR of 1.11 (95% CI: 1.05–1.19, 10 studies, 8,236 participants) (Figure 3). This suggests that patients who received reminders were, on average, 11% more likely to attend their appointments than those who did not. The range of RRs and their corresponding CIs across studies showed variability in the intervention outcomes. For example, Chen et al. [2018] reported a high RR of 3.05, indicating a strong improvement in attendance, whereas Ritchie et al. [2000], Lam et al. [2021] and Kwon et al. [2012] showed minimal effects, with RRs close to 1.0 (17,22,26). The meta-analysis test for overall effect resulted in Z=3.32, P<0.001 which further confirmed that the likelihood of this result reflecting random chance was minimal. However, heterogeneity was high, with an I² statistic of 83%, χ²=51.47, degrees of freedom (df) =9, P<0.001, indicating significant statistical variation across studies (15).

Figure 3 Forest plot illustrating the meta-analysis and heterogeneity results for attendance rates across the ten included studies. CI, confidence interval; df, degrees of freedom; M-H, Mantel-Haenszel random-effects.

SMS and phone reminders vs. no reminder

The subgroup analysis of SMS reminders vs. no reminder and phone call reminders vs. no reminders showed that both reminders led to improvements in attendance compared to no reminders. The SMS reminders achieved an overall RR of 1.14 (95% CI: 0.99–1.31, 4 studies, 4,636 participants), while phone call reminders had an RR of 1.11 (95% CI: 1.04–1.19, 5 studies, 3,369 participants) (Figure 4). Heterogeneity was greater in the SMS subgroup (I²=91%) than in the phone call subgroup (I²=63%). SMS reminders show a trend toward improved attendance, but the pooled effect did not reach conventional statistical significance at Z=1.84 (P=0.07) and varies considerably across studies. Telephone reminders are associated with a significant improvement in attendance at Z=3.08 (P=0.002), with a more consistent effect than SMS reminders.

Figure 4 Subgroup analysis of the effects of reminder interventions on patient attendance rates. CI, confidence interval; df, degrees of freedom; M-H, Mantel-Haenszel random-effects; SMS, short message service.

In a sensitivity analysis, the exclusion of individual studies was conducted to assess the robustness of the results and to check that no single study disproportionately influenced the overall effect size. However, the overall heterogeneity of the SMS reminder subgroup remained unaffected in sensitivity analysis, indicating that the findings were consistent across studies. Conversely, in the phone call reminder subgroup, Valero-Bover et al. [2022] (sample size =1,108) significantly contributed to heterogeneity; its exclusion reduced heterogeneity to 0% (8). Further examination of potential publication biases was conducted via Egger’s test for funnel plot asymmetry (Figure 5) with MedCalc software. The intercept value of 1.6845 with a 95% CI of −0.4633 to –3.8324 and a P value of 0.11 suggests no statistically significant evidence of small-study effects at the 0.05 level. A funnel plot was constructed to assess the potential for publication bias, with each study’s relative risk plotted against its corresponding SE. Ideally, in the absence of any publication bias, the plot would resemble a symmetrical, inverted funnel. However, the generated plot demonstrated asymmetry, which could reflect factors such as between-study heterogeneity, selective reporting, or random variation (14). Despite this visual asymmetry, Egger’s test was non-significant and therefore does not provide statistical evidence of publication bias affecting the overall findings (16). Most of the studies clustered near the pooled effect size in the top-central area of the plot, indicating a lower SE, while one outlier—Chen et al. [2018]—was positioned on the periphery, indicating potential variance in study outcomes (25). Given the relatively small number of studies and substantial heterogeneity, these tests have limited power and should be interpreted with caution.

Figure 5 Funnel plot assessing publication bias in studies evaluating the effectiveness of reminder interventions.

Discussion

This review explored the effectiveness of reminder interventions including telephone calls, SMS messages, and postal letters in improving outpatient attendance rates in hospital settings. The findings highlight that SMS and phone call reminders are more effective than usual care in improving attendance rates. Only one study was found exploring the effectiveness of postal reminders and positive outcomes were reported among these researchers also. Similar to prior reviews by Stubbs et al. [2012] and Guy et al. [2012], the findings from this review support the positive effects of these interventions on out-patient non-attendance (10,11). Stubbs et al. [2012] emphasized the context specific nature of interventions, noting differences in efficacy based on patient demographics and settings (11). This aligns with current review findings that SMS reminders were highly effective overall but demonstrated considerable variability in individual study reported outcomes (10,11). These are likely due to content and patient-specific factors (25). For example, among patients with diabetic retinopathy, SMS reminders containing tailored health information improved attendance rates more significantly than generic messages (25). The broader variability seen in SMS interventions may also reflect disparities in technology access and patient perceptions of text reminders. Stubbs et al. [2012] suggest that the effectiveness of SMS is seen more in younger versus older populations (11). However, this research is over a decade old, and patterns of mobile phone use have changed significantly since then, particularly among older age groups. This raises central questions about whether such age-related differences in response to SMS reminders persist. Future studies should consider exploring how changing technology adoption across age groups may influence the effectiveness of digital health interventions like SMS reminders.

Evaluation of impact of reminder interventions on patient attendance

The synthesized data from the studies in this review employed three primary types of reminder interventions: telephone calls, SMS, and postal letters. Attendance data from before and after the intervention phases were extracted to directly compare patients who received reminders (intervention groups) and those who did not (control groups). The analysis revealed that the type of reminder significantly affected patient attendance rates which can be further explored in various healthcare settings, departments, and regions. Subgroup analysis explored the impact of reminder type but did not directly compare SMS and telephone reminders. In subgroup analysis, the test for subgroup difference found that both SMS and phone calls were of benefit, with significant effects for telephone reminders. However, findings from individual studies provide contextual insights. For instance, in Guangdong, China, Chen et al. [2018] reported that SMS reminders were associated with a notable improvement in attendance rates from 14% to 42.9% suggesting potential benefit in low-resource environments (24). Consistent with effectiveness of SMS, a large quasi-randomized Hong Kong study in an endoscopy setting (Lam et al. 2021) used a single SMS 7–10 days pre-appointment that included date/time and bowel-prep instructions; attendance was 91.1% (983/1,079) with SMS vs. 88.1% (1,010/1,146) without, and there was a trend toward better bowel preparation quality (25). In contrast, Valero-Bover et al. [2022] observed substantial reductions in non-attendance within high income settings using telephone reminders, with decreases of 50.61% in dermatology and 39.33% in pneumonology departments. While these findings highlight the utility of both reminder types in their respective contexts, direct comparisons between SMS and telephone reminders were not assessed in the current meta-analysis. Further research is warranted to evaluate the relative effectives of different reminder modalities across diverse healthcare settings (8). Although less impactful overall, postal reminders were effective in highly structured environments, such as the orthodontic unit of the University Dental Hospital of Manchester, where post-intervention attendance increased from 64.7% to 73.0% (6). Although only one included study evaluated postal reminders, the absolute increase in attendance (64.7–73.0%) suggests that mailed prompts can be a viable option when digital coverage is low, patients may share devices, or confidentiality concerns limit mobile use (6). Postal reminders require minimal technological infrastructure, can be tailored to local languages and healthliteracy needs, and may therefore be well-suited to services or populations for whom SMS or telephone contact is unreliable or unacceptable. Future work should validate this signal in diverse hospital outpatient contexts and assess scalability alongside operational demands (6).

Non-attendance is multifactorial: patientlevel factors (e.g., age and socioeconomic constraints), logistical barriers (transport and travel distance), service features (lead time and scheduling flexibility), and contextual considerations (privacy with shared devices, cultural calendars) all influence response to reminders. These determinants vary across settings and should guide the choice and tailoring of reminder modality (SMS, telephone, postal) and message content (4,5,8,11,22,27). For instance, Lam et al. identified higher non-attendance among younger patients, those receiving social security assistance (underprivileged), and individuals with diabetes, highlighting the need to tailor reminders to socioeconomic and clinical risk profiles.

Timing also emerged as a critical factor influencing the effectiveness of reminder interventions. One of the studies in our review showed that strategically timed reminders, one week and three days before appointments, significantly improved attendance rates (25). This is consistent with a review by Boksmati et al. [2016] who recommend to optimize reminder timing, balancing the need to reduce appointment forgetfulness and allow rescheduling (28). Similarly, the findings of Robotham et al. [2016] on multiple notifications increasing attendance resonate with our observation that combining early and late reminders can maximize impact (27). However, none of the included studies explored the relationship between when appointments were scheduled and the reminder timing’s effectiveness, suggesting an area for future research.

This review supports the findings of the systematic review by Guy et al. [2012], who reported a significant improvement in attendance rates with SMS reminders (RR =1.48) (10). As per their conclusion, SMS reminders were found to be more cost-effective than telephone reminders, an observation corroborated by Boksmati et al. [2016] (28). However, the present review adds nuance by highlighting the role of context in interpreting effectiveness. While both SMS and telephone reminders were consistently more effective than no reminder across most studies, it is important to note that the populations in each subgroup differed. For example, SMS reminder studies every so often involved younger or low-resource populations, while telephone reminder studies were typically conducted in high-income, well-resourced settings. Therefore, though both modalities improved attendance, differences in demographic and healthcare infrastructure contexts limit direct comparisons. This emphasizes the need for future research comparing reminder types within similar population groups to determine the most appropriate intervention for specific settings.

Unlike SMS reminders, which face challenges like privacy and accessibility concerns, and varying acceptance among older patients, telephone reminders may benefit from their interactive nature and ability to address patient-specific queries in real time. This finding also aligns with Hasvold and Wootton’s [2011] suggestion that manual telephone reminders might have greater efficacy due to their personal touch (29). One of the studies in this review also highlighted concerns about shared mobile devices and confidentiality (21). These barriers were also noted by Boksmati et al. [2016], who emphasized the need for secure reminder systems to ensure patient trust and broader acceptance (28). Additionally, the heterogeneity observed in this review highlights the importance of considering demographic and socioeconomic factors when designing reminder systems. For instance, younger patients, who tend to have higher non-attendance rates-respond well to SMS reminders, as confirmed by Guy et al. [2012] (10). Conversely, older populations, with lower mobile phone ownership, may require alternative strategies such as phone calls or personalized postal letters.

This systematic review and meta-analysis present several strengths and limitations that affect the overall validity and applicability of the findings. A key strength lies in the exclusive inclusion of RCTs, which provide robust and high-quality evidence. Unlike earlier reviews that examined mixed settings, this review focused solely on RCTs conducted in hospital outpatient departments, offering a more targeted and clinically relevant perspective. The relatively large sample sizes in many of the included studies further strengthen the statistical power and reliability of the pooled results. Although considerable heterogeneity was observed in the meta-analysis, the absence of significant publication bias supports the credibility of the findings. Additionally, the inclusion of studies from diverse countries enhances the generalizability of the results across various healthcare systems. Nevertheless, some limitations must be acknowledged. This review focused on primary research and only focused on studies published in English, which might have limited the scope of the review. The exclusion of non-database sources may have constrained the search and analysis from evaluating the full range of interventions. A key gap in this review is the lack of formal economic evaluations of reminder strategies in hospital outpatient care. Three studies mentioned intervention costs, but none estimated savings from fewer missed appointments or the cost per extra attendance. This makes it hard for hospital managers to plan resources (e.g., staff time for calls, SMS platform fees, printing and postage). Future studies should build in simple, prospective cost analyses tracking fixed and variable costs, estimating savings from reduced no-shows and report results such as cost per additional attendance. Using consistent economic reporting across SMS, phone, and postal reminders would support context-specific adoption and scale-up.

Conclusions

This systematic review and meta-analysis provide evidence that appointment reminders-particularly SMS messages and telephone calls are beneficial in improving out-patient attendance rates in hospital settings. The findings suggest that both methods demonstrate substantial potential for improving attendance, with SMS offering a convenient and scalable option. As only one study was found that explored the effectiveness of postal reminders it is not possible to determine overall effectiveness in the context of this review. However, the finding form that one study was promising and indicates the need for further investigation of this reminder method. The meta-analysis revealed substantial heterogeneity across the included studies, indicating that reminder system effectiveness varies with contextual factors such as a population’s demographic characteristics, the healthcare infrastructure, and patients’ socioeconomic status. Despite this variability, the absence of significant publication bias contributes to the reliability of the findings. This review also emphasizes the need for secure reminder systems, as privacy concerns may hinder the widespread acceptance of reminders, particularly those delivered as SMS messages. The results support outcomes of previous research that demonstrate the positive impact of reminder interventions in reducing non-attendance while adding rigour by focusing exclusively on RCTs in hospital outpatient settings. The inclusion of diverse international studies increases the generalizability of the results.

Acknowledgments

The authors would like to express sincere gratitude to Mrs. Jessica Eustace-Cook, Subject Librarian at Trinity College Dublin, for her invaluable support and guidance.

Footnote

Reporting Checklist: The authors have completed the PRISMA reporting checklist. Available at https://jhmhp.amegroups.com/article/view/10.21037/jhmhp-25-51/rc

Peer Review File: Available at https://jhmhp.amegroups.com/article/view/10.21037/jhmhp-25-51/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jhmhp.amegroups.com/article/view/10.21037/jhmhp-25-51/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. Byrne AL, Baldwin A, Harvey C, et al. Understanding the impact and causes of 'failure to attend' on continuity of care for patients with chronic conditions. PLoS One 2021;16:e0247914. [Crossref] [PubMed]
2. Lee KS, Quintiliani L, Heinz A, et al. A financial incentive program to improve appointment attendance at a safety-net hospital-based primary care hepatitis C treatment program. PLoS One 2020;15:e0228767. [Crossref] [PubMed]
3. Blæhr EE, Søgaard R, Kristensen T, et al. Observational study identifies non-attendance characteristics in two hospital outpatient clinics. Dan Med J 2016;63:A5283.
4. Chaiyachati KH, Hubbard RA, Yeager A, et al. Rideshare-Based Medical Transportation for Medicaid Patients and Primary Care Show Rates: A Difference-in-Difference Analysis of a Pilot Program. J Gen Intern Med 2018;33:863-8. [Crossref] [PubMed]
5. Gatrad AR. A completed audit to reduce hospital outpatients non-attendance rates. Arch Dis Child 2000;82:59-61. [Crossref] [PubMed]
6. Can S, Macfarlane T, O'Brien KD. The use of postal reminders to reduce non-attendance at an orthodontic clinic: a randomised controlled trial. Br Dent J 2003;195:199-201; discussion 196. [Crossref] [PubMed]
7. Lagman RL, Samala RV, LeGrand S, et al. "If You Call Them, They Will Come": A Telephone Call Reminder to Decrease the No-Show Rate in an Outpatient Palliative Medicine Clinic. Am J Hosp Palliat Care 2021;38:448-51. [Crossref] [PubMed]
8. Valero-Bover D, González P, Carot-Sans G, et al. Reducing non-attendance in outpatient appointments: predictive model development, validation, and clinical assessment. BMC Health Serv Res 2022;22:451. [Crossref] [PubMed]
9. Tan J, Christie A, Montalvo SK, et al. Automated Text Message Reminders Improve Radiation Therapy Compliance. Int J Radiat Oncol Biol Phys 2019;103:1045-52. [Crossref] [PubMed]
10. Guy R, Hocking J, Wand H, et al. How effective are short message service reminders at increasing clinic attendance? A meta-analysis and systematic review. Health Serv Res 2012;47:614-32. [Crossref] [PubMed]
11. Stubbs ND, Geraci SA, Stephenson PL, et al. Methods to reduce outpatient non-attendance. Am J Med Sci 2012;344:211-9. [Crossref] [PubMed]
12. Ouzzani M, Hammady H, Fedorowicz Z, et al. Rayyan-a web and mobile app for systematic reviews. Syst Rev 2016;5:210. [Crossref] [PubMed]
13. Tawfik GM, Dila KAS, Mohamed MYF, et al. A step by step guide for conducting a systematic review and meta-analysis with simulation data. Trop Med Health 2019;47:46. [Crossref] [PubMed]
14. Higgins J, Thomas J, editors. Cochrane Handbook for Systematic Reviews of Interventions. London: Cochrane Training; 2023.
15. WestSLGartlehnerGMansfieldAJ2010.
16. Lin L, Chu H. Quantifying publication bias in meta-analysis. Biometrics 2018;74:785-94. [Crossref] [PubMed]
17. Roberts N, Meade K, Partridge M. The effect of telephone reminders on attendance in respiratory outpatient clinics. J Health Serv Res Policy 2007;12:69-72. [Crossref] [PubMed]
18. Kwon SB. The effect of telephone call reminders on electrodiagnostic laboratory attendance in Korea. Healthmed 2012;6:2850-5.
19. Shah SJ, Cronin P, Hong CS, et al. Targeted Reminder Phone Calls to Patients at High Risk of No-Show for Primary Care Appointment: A Randomized Trial. J Gen Intern Med 2016;31:1460-6. [Crossref] [PubMed]
20. Andreae MH, Nair S, Gabry JS, et al. A pragmatic trial to improve adherence with scheduled appointments in an inner-city pain clinic by human phone calls in the patient's preferred language. J Clin Anesth 2017;42:77-83. [Crossref] [PubMed]
21. Youssef AB, Alharthi H, Khaldi OA, et al. Effectiveness of text message reminders on nonattendance of outpatient clinic appointments in three different specialties: A randomized controlled trial in a Saudi hospital. J Taibah Univ Med Sci 2014;9:23-9.
22. Low PT, Ng CG, Kadir MS, et al. Reminder through mobile messaging application improves outpatient attendance and medication adherence among patients with depression: An open-label randomised controlled trial. Med J Malaysia 2021;76:617-23.
23. Ritchie PD, Jenkins M, Cameron PA. A telephone call reminder to improve outpatient attendance in patients referred from the emergency department: a randomised controlled trial. Aust N Z J Med 2000;30:585-92. [Crossref] [PubMed]
24. Taylor NF, Bottrell J, Lawler K, et al. Mobile telephone short message service reminders can reduce nonattendance in physical therapy outpatient clinics: a randomized controlled trial. Arch Phys Med Rehabil 2012;93:21-6. [Crossref] [PubMed]
25. Chen T, Zhu W, Tang B, et al. A Mobile Phone Informational Reminder to Improve Eye Care Adherence Among Diabetic Patients in Rural China: A Randomized Controlled Trial. Am J Ophthalmol 2018;194:54-62. [Crossref] [PubMed]
26. Lam TYT, Hui AJ, Sia F, et al. Short Message Service reminders reduce outpatient colonoscopy nonattendance rate: A randomized controlled study. J Gastroenterol Hepatol 2021;36:1044-50. [Crossref] [PubMed]
27. Robotham D, Satkunanathan S, Reynolds J, et al. Using digital notifications to improve attendance in clinic: systematic review and meta-analysis. BMJ Open 2016;6:e012116. [Crossref] [PubMed]
28. Boksmati N, Butler-Henderson K, Anderson K, et al. The Effectiveness of SMS Reminders on Appointment Attendance: a Meta-Analysis. J Med Syst 2016;40:90. [Crossref] [PubMed]
29. Hasvold PE, Wootton R. Use of telephone and SMS reminders to improve attendance at hospital appointments: a systematic review. J Telemed Telecare 2011;17:358-64. [Crossref] [PubMed]