Background and objective: To test the reliability and validity of 8-day and 30-day self-report measures of adherence to daily isoniazid (INH) for treatment of latent tuberculosis infection (LTBI).
Methods: Participants were 286 Latino adolescents (ages 13-18, 55.6% male) with LTBI recruited from 10 public middle and high schools in San Diego County. INH adherence was measured monthly for up to 9 months by interview and urine specimens at unannounced visits. Reliability and validity analyses were performed within 5 consecutive months. Reliability was assessed by correlating: (1) 8- and 30-day INH adherence measures within each month; and (2) each of the two adherence measures across months. Validity was assessed by correlating reported measures with biological assays within each month.
Results: Reliability tests yielded significant correlation coefficients (p < .05 to .001), both across measures (r = 0.71-0.93) and across time (r = 0.29-0.64 for 8-day recall; r = 0.32-0.69 for 30-day recall). Validity tests of both adherence measures were also significant (p < .05 to .001): 8-day recall (r(pb) = 0.52-0.72) and 30-day recall (r(pb) = 0.37-0.71).
Conclusion: Results suggest that impromptu recall measures of INH adherence, combined with urine collection, are reliable and valid in Latino adolescents.