Simplification of isoniazid phenotyping procedure to promote its application in the chemotherapy of tuberculosis.

In this investigation a simple urine test for phenotyping isoniazid inactivators is evaluated. In the new method, isoniazid is artificially acetylated in urine and determined by the same colour reaction as that used for acetylisoniazid. Comparative studies showed that the test is reliable and can be performed with accuracy and ease even in poorly equipped laboratories. In contrast to other urine tests, it does not require an expensive spectrophotometer, tedious hydrolysis processing of the samples, or standard curves. The results can be read on a plain colorimeter, or even without any instrument.