IntroductionAlthough interactive voice response (IVR) is a promising mobile phone survey (MPS) method for public health data collection in low- and middle-income countries (LMICs), participation rates for this method remain lower than traditional methods. This study tested whether using different introductory messages increases the participation rates of IVR surveys in two LMICs, Bangladesh and Uganda.MethodsWe conducted two randomized, controlled micro-trials using fully-automated random digit dialing to test the impact of (1) the gender of the speaker recording the survey (i.e., survey voice); and (2) the valence of the invitation to participate in the survey (i.e., survey introduction) on response and cooperation rates. Participants indicated their consent by using the keypad of cellphones. Four study arms were compared: (1) male and informational (MI); (2) female and information (FI); (3) male and motivational (MM); and (4) female and motivational (FM).ResultsBangladesh and Uganda had 1705 and 1732 complete surveys, respectively. In both countries, a majority of the respondents were males, young adults (i.e., 18-29-year-olds), urban residents, and had O-level/above education level.In Bangladesh, the contact rate was higher in FI (48.9%), MM (50.0%), and FM (55.2%) groups than in MI (43.0%); the response rate was higher in FI (32.3%) and FM (33.1%) but not in MM (27.2%) and MI (27.1%). Some differences in cooperation and refusal rates were also observed. In Uganda, MM (65.4%) and FM (67.9%) had higher contact rates than MI (60.8%). The response rate was only higher in MI (52.5%) compared to MI (45.9%). Refusal and cooperation rates were similar.In Bangladesh, after pooling by introductions, female arms had higher contact (52.1% vs 46.5%), response (32.7% vs 27.1%), and cooperation (47.8% vs 40.4%) rates than male arms. Pooling by gender showed higher contact (52.3% vs 45.6%) and refusal (22.5% vs 16.3%) rates but lower cooperation rate (40.0% vs 48.2%) in motivational arms than informational arms. In Uganda, pooling intros did not show any difference in survey rates by gender; however, pooling by intros showed higher contact (66.5% vs 61.5%) and response (50.0% vs 45.2%) rates in motivational arms than informational arms.ConclusionOverall, we found higher survey rates among female voice and motivational introduction arms compared to male voice and informational introduction arm in Bangladesh. However, Uganda had higher rates for motivational intro arms only compared to informational arms. Gender and valence must be considered for successful IVR surveys.Trial registrationName of the registry: ClinicalTrials.gov. Trial registration number:NCT03772431. Date of registration: 12/11/2018, Retrospectively Registered. URL of trial registry record:https://clinicaltrials.gov/ct2/show/NCT03772431?term=03772431&cond=Non-Communicable+Disease&draw=2&rank=1. Protocol Availability:https://www.researchprotocols.org/2017/5/e81.