Use of the urine color test to monitor compliance with isoniazid treatment of latent tuberculosis infection

Study objective: To apply the Arkansas color method in order to evaluate drug compliance and factors that can predict treatment adherence in patients being treated for latent tuberculosis infection (LTBI) with a single daily dose of isoniazid (INH). Design: Prospective study of adherence of 105 patients aged 1 to 75 years who were treated with a single daily dose of INH for LTBI. Interventions: Patients or their parents were interviewed regarding parameters that may affect compliance. Urine samples were collected and tested for INH metabolites with the Arkansas color method. Results: Nonadherence to treatment was found in 28.5% of patients. There was no statistically significant correlation among the following parameters: gender; age; diagnosis; mode of administration (self or parents); duration of treatment; dose of INH per weight; or interval since last intake of dose. Twenty-six patients were randomly checked for treatment adherence on two separate visits, and nonadherent patients were informed immediately and their condition was fully explained to them. Five of six patients who were nonadherent in the first visit and were examined twice became adherent in the second visit. Three of 20 patients who were adherent in the first visit became nonadherent. Conclusion: Almost one third of the patients who received LTBI treatment with INH were nonadherent to treatment. No factor was found to predict adherence. The Arkansas method can be used by the family physician and is a simple, immediate method to follow-up patients with LTBI who are treated with INH.