The design rests on a three-arm, randomized controlled trial with two intervention arms and one control group. The trial shall be single-blinded where the investigators and participants shall not be blinded to the intervention, whereas interviewers and data analysts will be blinded to group allocation. The intervention shall include the use of mobile cellphone SMS in addition to the standard of care provided to the clients. Participants shall be randomly allocated in a 1:1:1 ratio to one of three arms prior to the beginning of the intervention: (1) once weekly mobile phone SMS, (2) twice weekly mobile phone SMS, and (3) a control group that shall not receive mobile cellphone SMS. Clients will be recruited from the government-approved centers of the Regional Hospital Buea and Regional Hospital Limbe providing HIV treatment services.

This is a parallel-group design evaluating the effects of adding once-weekly mobile phone text messages and twice-weekly mobile phone text messages to the usual standard of care (intervention) versus usual standard of care alone (control) among HIV clients receiving ART. Eligible and consenting participants shall be randomized to interventions and control arms using a 1:1:1 allocation ratio by the opaque sealed envelope method. A computer-generated randomization list will be produced using random block sizes of 2, 4, and 6 by the research biostatistician. The allocation codes shall then be put in serially numbered opaque sealed envelopes and administered by the research staff at the various hospitals. Trained interviewers, who shall be blinded to group allocation, will collect data using pretested questionnaires containing sociodemographic data, clinical information, retention, and adherence measures at baseline and at 2, 4, and 6 months. The biostatistician shall also be blinded to group allocation. Blood samples will be collected and analyzed for viral load during the trial once a participant has been on ART for at least 6 months. The time schedule of enrollment, interventions, and assessments are summarized in Figure 1.

Cameroon is a sub-Saharan central African country made of ten regions and a population of over 24 million inhabitants [21]. The study will be implemented in Fako Division of the South West Region of Cameroon. The adult prevalence of HIV in the country was 3.4% in 2018 [22]. The adult prevalence of HIV in the South West Region was 3.6% in 2018 [22]. Most inhabitants practice agriculture as the main economic activity. The region has two seasons: the dry season from October to March and the wet season from April to September. Almost all ethnic groups in Cameroon are represented in the region, attracted by the fertile volcanic soil and the Cameroon Development Corporation, a giant agricultural corporation that seconds the state of Cameroon in employment. The two hospitals selected for the trial have government-approved centers offering free treatment and care services for HIV to the population of the region. Participants will be residents in their various communities and support groups while visiting these treatment hospitals for routine care during the entire study period. As per the Cameroonian Ministry of Public Health national guidelines, newly diagnosed clients are initiated on free nonnucleotide reverse transcriptase inhibitors–based ART irrespective of their viral load count or CD₄⁺ T cell count [11]. Recently, HIV clients initiating ART were systematically placed on isoniazid prophylaxis for the first 6 months of their ART. These are the largest treatment centers in the region and offer enormous potential for recruitment.

The study population shall include HIV clients either coinfected with or without tuberculosis who come to the hospital for a routine health evaluation. Participants shall be consecutively recruited and randomly allocated to the intervention and control groups.

We shall include clients who are 21 years or older, have access to or own a mobile phone and can read text messages, and who have been on ART for at least a month and planned to live in Cameroon during the period of the study. We shall place more emphasis on clients who have started ART for at least 1 month to measure the differential effects for clients initiating ART versus those who have been under treatment for longer durations. Informed consent is a prerequisite for participating in the study and shall be provided orally and in writing.

We shall exclude clients who have been on ART for less than a month and who are younger than 21 years. Clients who have used ART for at least 1 month are chosen to enable us to be able to calculate a baseline figure for treatment adherence.

The HIV clients will be receiving ART for free from the hospital staff at the HIV treatment centers. The HIV clients who shall be coinfected with tuberculosis shall also receive directly observed treatment short-course for free. This is the usual standard of care for people living with HIV/AIDS and tuberculosis in Cameroon [23]. Patients with HIV on any of these treatments shall be randomized to receive mobile phone text message reminders. The trial shall comprise 2 intervention groups and 1 control group to investigate the impact of text message reminders on retention in care and adherence to treatment and health outcomes.

A short text message will be sent to the participants in the intervention groups in English or French depending on the preferred language of each client. The content of these text messages has been developed and pretested in focus group discussions involving people living with HIV/AIDS, their caregivers, and health care workers. The construct of the health belief model was used to develop these text messages that are sociocultural acceptable and targeted at improving retention in care and promoting adherence to treatment [24]. The messages are motivating and shall act both as reminders and a cue to action. Participants unanimously agreed that the messages should not contain the name of the disease. It was also concluded that the word “food” should be used in place of medication or drug when sending the messages (Textbox 1). The message shall also contain a phone number that the participants can call back if they need directives on their treatment and care. The content shall be varied so as to retain participants’ attention and interest throughout the period of the study and to explore the various aspects of behavior change. There shall be a list of phone numbers that the messages targeted at improving retention in care shall be sent midway before the next clinic visit schedule and then 2 days before each clinic visit appointment. The messages targeted at promoting adherence to treatment will be sent twice every week. The “delivery report” function of the mobile phone shall be used to verify and to record whether the messages have been delivered to the clients. Clients will be contacted through the phone numbers of their contact persons in the event of undelivered messages. The issue of missing phone numbers shall be resolved by replacing clients’ existing contracts with their recent phone numbers. One message will be sent per week in the evening between 6 PM and 7 PM of a day chosen by the client in the once-weekly SMS intervention arm. In addition, two messages shall be sent per week in the evening between 6 PM and 7 PM of 2 days chosen by the client in the twice-weekly SMS intervention arm. The mobile phone text messaging shall be provided as add-ons to the usual standard of care, which includes rare ART counseling and occasional home visits.

The routine practice in Cameroon is that, at ART initiation, the responsibilities of the treatment centers usually explain the side effects of medications and problems associated with poor adherence to the clients prior to dispensing drugs. All participants including those in the control arm have received this educational message during their routine hospital visits. Participants randomly allocated to the control group shall not receive mobile phone SMS. However, they shall receive ART, be screened for tuberculosis coinfection, and be interviewed alongside the other participants.

The trial shall run for 6 months. Outcome assessments will be conducted at baseline, 2 months, 4 months, and 6 months.

The sample size determination is based on the test of the null hypothesis that the rates of adherence to ART in the intervention and control groups are equal. The primary measure of effect is the rate of adherence to ART as measured by using the VAS over 6 months. Given the information from previous studies [10,11], it is estimated that approximately 60% of participants would maintain adherence ≥95% without intervention and that the interventions would help 82% of the participants maintain ≥95% adherence. A two-sided test is assumed where an effect in either direction will be interpreted at a significance level of 5%. The study will have a power of 80% to yield a statistically significant result using a chi-square test (assuming an intention-to-treat principle for the analysis) of the relative risk at an alpha level of 5% to detect a 25% difference (60% vs 85%).

The formula for calculating the sample size for randomized controlled trials by Chan [26] is used.

where c=7.9 for 80% power and p1 and p2 are the proportion estimates (60% for the control group and 85% for the intervention group).

It is assumed that 10% of the participants shall drop out of the study due to loss to follow-up and mortality. A total of 52 participants shall be randomized to each arm to allow for the 10% drop out. Therefore, the required sample size will be 156 (52 x 3 = 156) participants.

The CONSORT (Consolidated Standards of Reporting Trials) guidelines will be used in reporting the results. The biostatistician shall be blinded to the group allocation. The process of client selection and flow throughout the study will be summarized using a flow diagram. The analysis of client demographics and outcome variables shall be summarized using descriptive summary measures, expressed as mean (standard deviation) or median (range) for continuous variables and number (percentages) for categorical variables. All outcomes shall be analyzed using an intention-to-treat principle where data from participants shall be analyzed according to the group to which they were randomized even if they do not receive the allocated intervention. Missing data shall be handled using the multiple-imputation method. The student t test and analysis of variance for comparing group means will be used. All statistical tests shall be performed using two-sided tests at the 5% level of significance. The Bonferroni method shall be used to adjust the level of significance for testing of secondary outcomes to keep the overall level at an alpha of 5%. For all group comparisons, the results shall be expressed as an effect (or risk ratio for binary outcomes), corresponding two-sided 95% confidence intervals, and associated P values. P values shall be reported to three decimal places with values less than .001 reported as <.001. Adjusted analyses using baseline variables shall be performed using regression techniques to determine the continuing influence of key baseline characteristics on the outcomes. The Kaplan-Meier survival analysis will be used for timed variables like mortality. All analyses will be performed using SPSS version 25.0 (IBM Corp) for Windows. Adherence will be measured both as a continuous outcome (change in adherence) and as a binary outcome (ie, adherent, 95% of pills taken, or nonadherent, <95% of pills taken) following the composite adherence score method. Adherence data shall be handled in a number of ways, reported as the number of doses respected, and shall be combined into a composite score. The effects of the intervention shall be reported on all the measures of adherence used and will be compared for discrepancies.

This study was conceived and designed to address gaps in the care and support available to people living with HIV/AIDS who are receiving ART. The intervention was designed with the active involvement of patients with HIV, their caregivers, and health workers through focus group discussions. Our randomized controlled trial offers participants the opportunity to provide feedback regarding the burden of the intervention through focus group discussions involving a cross-section of participants.

Ethical clearance for this trial was obtained from the Institutional Review Board of the Faculty of Health Sciences of the University of Buea in Cameroon (Reference number: 2018/147/UB/SG/IRB/FHS). Administrative authorization was obtained from the Regional Delegation of the Ministry of Public Health for the South West Region and the District Health Services. The purpose of the study and the role of the participants will be well explained in the consent form to the participants and participation shall only take place after the participant has read and signed the informed consent forms voluntarily. The informed consent shall include signed permission to consult the client’s medical records over the duration of the study.

Dissemination efforts shall target individuals and institutions that will have the most impact on local, national, and international HIV and AIDS policies. Therefore, dissemination plans shall include the presentation of research findings in seminars, conferences, and scientific publications in peer-reviewed journals. A summary of the findings will be made available to participants.