Point-of-care Arkansas method for measuring adherence to treatment with isoniazid

Abstract

Summary We evaluated the accuracy of a point-of-care test designed to measure adherence to isoniazid (INH) preventive therapy in a hospital setting in Rio de Janeiro, Brazil. Patients on treatment with daily INH and patients not receiving INH were included. Sensitivity and specificity of the test were 84%/98% at the first minute, and 95%/98% at the fifth minute, respectively. Among smokers, sensitivity and specificity was reduced (80%/89% at the fifth minute, respectively), but only 17% smoked. This test accurately detected INH metabolites 24 hours following directly observed INH intake, though sensitivity and specificity may be compromised by tobacco smoke exposure.

Adherence to Tuberculosis Therapy among Patients Receiving Home-Based Directly Observed Treatment: Evidence from the United Republic of Tanzania

“…This point-of-care test detects isoniazid and its metabolites in the patient's urine with high sensitivity and specificity [20], confirming whether isoniazid has been taken in the last 24 to 30 hours. It takes only 5 minutes to perform and does not require laboratory facilities, so can be undertaken in the patient's home.…”

Point-of-care urine test for assessing adherence to isoniazid treatment for tuberculosis

“…Similarly, 75% of a South Indian population were slow acetylators [10]. Fast acetylation was postulated as an explanation for negative urine results at 24 h in five out of 94 patients after isoniazid ingestion, although acetylator status was not measured [4]. Using logistic regression analysis, we found no effect on Isoscreen results in five fast acetylators, whose individual results did not differ from others.…”

“…Purple or blue samples are deemed positive, green intermediate and yellow negative. High sensitivities and specificities have been reported, but without a consistent relationship to the timing of the previous dose of isoniazid or measurement of acetylator status [2,4].…”

Isoniazid/acetylisoniazid urine concentrations: markers of adherence to isoniazid preventive therapy in children

“…The range of colours observed is reported in the Figure. Based on reports from previous studies, 3-7 and supported by high-performance liquid chromatography-mass spectrometry (HPLC-MS/MS) findings, yellow was defined as negative, while the other colours in the Figure were recorded as positive.…”

“…1 Adherence to therapy is important for efficacy. 2 The Arkansas method is a qualitative urine assay used to monitor isoniazid (INH) ingestion 3-7 by detecting urinary metabolites reacting with cyanogen chloride and barbituric acid, to produce a blue-purple dye indicating a positive reaction. 8 A limitation of the test is that its sensitivity decreases with increasing time after INH ingestion.…”