Pharmacy refill rates and urine testing for isoniazid metabolites among participants of the Botswana Isoniazid Preventive Therapy Trial, 2004–2008.

*Unannounced, urine samples were collected in 2006, 2007 and 2008 from 200 randomly selected participants receiving isoniazid who returned for refills. The numbers of participants and their median (range) month in the study were:194 at month 13† (5–22), 202 at month 22‡ (12–30), 195 at month 30§ (21–36). Abbreviations: 6H = six months of isoniazid daily followed by placebo; 36H = 36 months of isoniazid daily.