The reliability and practicality of the Arkansas method assay of isoniazid adherence

The Arkansas method (AM) for isoniazid (INH) metabolite detection is a relatively inexpensive, simple, objective measure of adherence. The purpose of the study was to explore whether variations in urine sample handling and storage will produce accurate assay outcomes. Participants were a convenience sample of 28 adults and adolescents prescribed INH for latent tuberculosis infection. Participants provided one sample to test effects of the following: mixing processes; durations at room temperature, in a refrigerator, or frozen; and effects of freeze/thaw cycles on AM outcomes. No manipulations had a discernible impact on outcomes with concordant positive rates from 85% to 100%. Concordance rates of manipulated samples did not appear to differ from rates of norm samples. Results suggest that urine samples can withstand a variety of manipulations in both handling and storage without affecting the accuracy of AM assay results. These findings have important implications for providers of treatment and researchers and provide the impetus for both to examine the potential of using the AM of INH metabolite testing as a measure of medication adherence.