KHARBANDA ET AL. RESPOND

We commend Maher et al. for their novel use of text messaging to contact difficult-to-reach study participants. We agree that text messaging is a powerful tool to recruit study participants and reduce drop-out rates among persons participating in longitudinal assessments. These strategies rely on participants being able to open, read, and respond to text messages. In our focus groups we observed many parents having difficulties responding to interactive text messages,1 but in our ongoing work we have found that participants of varied ages are responding at rates higher than expected. Using input from our qualitative evaluation,1 we have developed and implemented several text messaging interventions to improve immunization coverage among urban children and adolescents. We were pleased to note that of the 124 parents who received our text message reminders, 36 (29%) responded to an interactive text and said that they liked our service. In a second study, of 110 older adults with heart disease (mean age = 62 years), 34% responded to an interactive text message.2 In a third study, 87% of 101 young urban women participating in research using text messaging to promote contraceptive adherence responded to 1 or more text message queries. (R. Andres, PhD, Columbia University, personal communication). These preliminary studies suggest that text messaging can be an effective and well-accepted method for sending and receiving information for research, clinical, or public health applications. While 89% of persons in the United States own a cell phone,3 cell phone penetration is even higher in underserved populations.4 Thus, we agree with Maher et al. that text messaging may be particularly useful for targeting difficult-to-reach populations. As text messaging is still a novel research tool, further work is needed to determine optimal strategies for creating and implementing these interventions.