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Mhealth. 2019 Jun 18;5:17. doi: 10.21037/mhealth.2019.06.01. eCollection 2019.

Methods, system errors, and demographic differences in participant errors using daily text message-based short message service computer-assisted self-interview (SMS-CASI) to measure sexual risk behavior in a RCT of HIV self-test use.

Author information

Center for AIDS Prevention Studies, Department of Medicine, University of California San Francisco, San Francisco, CA, USA.
Center for Vulnerable Populations at Zuckerberg San Francisco General Hospital and Trauma Center, Division of General Internal Medicine, Department of Medicine, School of Medicine, University of California San Francisco, San Francisco, CA, USA.
Bakar Computational Health Science Institute, University of California San Francisco, San Francisco, CA, USA.
HIV Center for Clinical and Behavioral Studies, Division of Gender, Sexuality and Health, NY State Psychiatric Institute and Columbia University, New York, NY, USA.
Department of Psychology, Syracuse University, Syracuse, USA.
Department of Community Health and Social Sciences, CUNY Graduate School of Public Health and Health Policy, New York, NY, USA.
Department of Pediatrics, University of Puerto Rico Medical Sciences Campus, San Juan, USA.



Assessment of sexual risk behavior is crucial to HIV prevention trials. Currently, there are no biomarkers or objective measures to detect and characterize sexual risk behavior; therefore, we must rely on self-reports. Self-report accuracy may be improved by collecting data in real-time. Our objective was to demonstrate how a text message-based short message service computer-assisted self-interview (SMS-CASI) system can collect daily sexual risk behavior data.


During the course of a 2-arm randomized controlled trial, confidential daily SMS-CASI was used to assess sexual risk behavior over three months for participants using only condoms in the control condition and using condoms and HIV self-tests to test themselves and their non-monogamous sexual partner over six months for participants in the intervention condition (total N=272). Active monitoring of participants responses and data cleaning took place concurrently with trial execution. Descriptive statistics were used to examine frequencies related to system functionality, participant reporting, system errors, communication patterns, and overall feasibility of using the SMS-CASI system for reporting sexual risk behavior.


The SMS-CASI system processed 272,565 messages. In addition, 87 classifications of metadata were collected, for a total of 22,895,460 different data points. Types of messages included these sent (N=171,749; 63.01%) to participants, received (N=100,646; 36.93%) from participants, and failed (N=168; 0.06%) to be sent. Most errors (N=1,858) were due to system malfunctions (N=535; 28.79%) or participants' mistakes (N=1,289; 69.38%). Participant errors included: wrong password, incomplete surveys, and invalid response. The highest error rates by demographic characteristics were by age among older participants [ages 30-39; 383 errors (29.71%), and 40-69; 545 errors (42.28%)] and by race among Hispanic/Latino participants [487 errors (37.78%)].


The SMS-CASI system was effective at confidentially collecting sexual risk behavior data on a daily basis, potentially contributing to reduced recall and social desirability bias. This study provides methodological examples and data demonstrating how SMS-CASI can be used for sexual health data collection.


HIV home testing; computer-assisted self-interview (CASI); mHealth; text messaging short message service (SMS)

Conflict of interest statement

Conflicts of Interest: The authors have no conflicts of interest to declare.

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