Background

This pilot study evaluates the effectiveness of mobile talk-time incentives in promoting sustained participation in a longitudinal mHealth data collection program among people living with HIV in Lusaka, Zambia. With mobile device usage rapidly increasing in sub-Saharan Africa, mHealth tools, like mobile phone surveys, present an opportunity to capture vital health feedback and improve patient monitoring however, evidence on optimal incentive strategies to ensure long-term engagement remains limited. Understanding response patterns across multiple survey rounds, provides valuable insights into incentive strategies for long-term participation in mHealth programs within the context of expanding mobile access but prepaid billing and multi-SIM usage practices in Zambia and the broader sub-Saharan Africa (SSA) region.

Objective

Assess the response rate success across multiple invitations to participate in a care experience survey using a mobile phone short code and USSD model among individuals in an HIV care setting in the Lusaka Province of Zambia.

Methods

We enrolled study participants among individuals exiting two study clinics, one in a peri-urban setting and one in an urban setting. Two rounds of survey invitations were sent to those enrolled in the study. The first invitation was distributed between 1 November 2018 and 25 June 2019 with the invitation to the second survey round following three months after the first (1 February 2019 to 23 September 2019). Three incentive levels were randomly assigned by participant and survey round 1) no incentive, 2) two Zambian Kwacha (ZMW) (~0.16 USD), and 3) five ZMW (~0.42 USD). We assessed the association between incentive and response to the survey using a mixed effects Poisson regression model allowing random effects at the individual and facility level. Probability plots for survey completion were generated based on language, incentive level, and survey round. We projected the cost per additional response for different incentive levels.

Results

A total of 1,006 participants were enrolled of which 72.1% occurred in the urban HIV care facility and 62.2% requested survey be sent in English. We sent a total of 1,992 survey invitations for both rounds. Overall, survey completion across both surveys was 32.1%, with significantly different response rates between the first (40.5%, 95% confidence interval [CI]: 37.4, 43.6%) and second (23.7%, 95% CI: 21.1, 26.4%) invitations. Implementing a 5 ZMW incentive significantly increased adjusted prevalence ratio (aPR) for survey completion compared to those that received no incentive (aPR: 1.35; 95% CI: (1.11, 1.63). The cost per additional response highest at 5 ZMW (72.8 ZMW).

 Conclusion

We observed a sharp decline of almost fifty percent in survey completion success from initial invitation to follow-up survey administered three months later. This substantial decrease suggests that longitudinal data collection potential for a care experience survey may be limited without additional sensitization and/or survey reminders. Implementing a moderate incentive increased response rates to our healthcare experience survey. Tailoring survey strategies to accommodate language preferences and providing moderate incentives can optimize response rates in Zambia.

Recruitment procedure

Potential survey participants were identified by research assistants at one of two (one in an urban setting, one in a peri-urban setting) pilot study HIV care facilities using convenience sampling following reception and triage procedures including routine data collection (e.g., temperature, weight, and blood pressure). Eligibility for study participation was limited to individuals who were enrolled as a recipient of care at the study facility, were aged 18 years or older, self-reported as literate in one of four survey languages, possessed a mobile phone during enrollment, and voluntarily consented to participate in the study. We confirmed that the mobile phone number reported by the potential participant belonged to the individual through a registration process using the unique PCPH short code, *744# on the potential participant’s phone at enrollment. The registration process confirmed ability to initiate and complete a USSD session, collected the language preference, and recorded the facility where the enrolment took place.

Data collection

Survey participants were presented with 4 questions related to their experience at their most recent HIV care visit. The opening question was the same for all participants, the next 3 questions were drawn, using a systematic algorithm, from a bank of 9 questions. Survey questions were subject to a cognitive interviewing process to increase acceptability, understanding, and appropriateness prior to piloting. At enrollment, participants selected their preferred survey language from English, Bemba spoken by 33.5% of the Zambian population, Nyanja, spoken by 14.8% of the Zambian population, or Tonga, spoken by 11.4% of the Zambian population. Only 2% of the population have English as the first language however, English is the most spoken second language.