Evaluating Urine Isoniazid Testing to Detect Nonadherence to Tuberculosis Medications in India

Developed by Arkansas' Public Health Service in the 1970s, this test detects metabolites of isoniazid, a drug present in drug-susceptible TB regimens. IsoScreen (GFC Diagnostics, UK) is a commercial version of the Arkansas method with reagents enclosed in a plastic vial, into which 2mL of urine can be injected with a syringe. If the urine contains isoniazid, reagents turn purple/blue (suggesting a dose was taken in the last 24 hours or appropriate adherence) or green (suggesting a dose was taken 24-48 hours before or one missed dose). A yellow result (no color change) suggests medication has not been taken for \>48 hours (two or more missed doses).