SMS-text Adherence Support (StAR*) Study, a Randomized Three-arm Open Parallel Group Trial to Evaluate the Effects of a Structured Programme of Hypertension Treatment Adherence Support Delivered Remotely Through SMS-text Messages on Blood Pressure at 12 Months as Compared With Usual Care.

General synopsis for SMS-text Adherence Support (*StAR) Study and associated preparatory and pilot work

Background: High blood pressure is an important risk factor for heart disease, stroke and chronic kidney disease. Clear evidence exists that for individuals with high blood pressure (hypertension) lowering blood pressure really reduces this risk. One of the critical factors in the long term control of blood pressure is the regular use of effective antihypertensive medications. In South Africa, poor treatment adherence (attending clinic, re-filling prescriptions, and regularly taking hypertension tablets) is known to be an important and alterable risk factor for uncontrolled high blood pressure and its complications (heart disease, stroke and chronic kidney disease). SMS-text messages have been shown to improve clinic attendance and medication adherence for some diseases (like HIV and TB) in other low-resource settings. It is not clear whether SMS-text messages to support treatment adherence have an effect on long-term blood pressure control. The acceptability, sustainability and scalability such technology also remains to be determined.

Aim: To investigate if a system of SMS-text messages to support treatment adherence is more effective than usual care for controlling high blood-pressure.

Objectives: The main objective is to test whether advice and support given by SMS-text, either by providing information (informational) or by allowing a two-way communication (interactive) improves control of blood pressure at one year compared to usual care.

Additional objectives include assessing whether the interventions have an effect on,

• Clinic attendance
• Prescription refill adherence
• Self-reported medication adherence
• Hypertension related illness or death
• Patient empowerment

Study design: Single centre randomized three-arm parallel group trial As it is not clear how best to support treatment adherence for people with hypertension we need to compare the different ways this might be done. Eligible patients who provide written consent will be put into one of three groups and then compared. The groups are selected by a computer which has no information about the individual (i.e. by chance). Participants in each group will get different types of SMS-text messages and these are compared.

Study interventions:

• Enhanced usual care In addition to their usual clinical care participants will receive the pre-randomisation "Welcome to the *StAR Study" SMS-text, a "Happy Birthday" SMS-text on their date of birth and up to six additional SMS-text messages containing study specific information and thanking the participant for taking part in the study.
• Informational SMS-text messages In addition to enhanced usual care, participants allocated to the informational SMS-text support group will receive semi-tailored structured adherence-support (including clinic appointment and medication pick-up reminders, medication adherence support and hypertension-related education.)
• Interactive SMS-text messages In addition to enhanced usual care and informational SMS-text messages, SMS-text messages sent to participants in the interactive SMS-text group will contain a "prompt to respond" which will guide participants to additional SMS-text based resources.

Outcome measures: The main outcome measure is mean blood pressure measured at one year. Additional outcomes include the proportion of participants with "controlled blood pressure" as well as measures of clinic attendance, prescription refill adherence, self-reported medication adherence, hypertension related illness or death, and patient empowerment.