The investigators will consent and enroll participants at the time of laboratory testing for cluster of differentiation 4 (CD4) count, viral loads, acid fast bacteria smears of sputum, among others. Those with abnormal results will be randomized to various messaging formats and receive text messages requesting a prompt return to clinic. For outcomes, the investigators will measure successful receipt and comprehension of messages, as well as proportion returning within 14 days of the abnormal laboratory test.