Evaluation of the Arkansas method of urine testing for isoniazid in South Africa.
METHODS
A South African hospital serving gold mine employees.


OBJECTIVE
To determine the sensitivity and specificity of the Arkansas method for detecting isoniazid (INH) metabolites among South African adults and to examine the effect of smoking status on positive results.


METHODS
Urine specimens were collected from in-patients taking INH as part of tuberculosis treatment at 6, 12 and 24 h after a directly observed 300 mg oral dose. As a control group, a single urine specimen was collected from surgical in-patients not taking INH. Specimens were tested for INH using a commercially available dipstick.


RESULTS
A total of 153 patients on INH and 60 controls were recruited. The sensitivity of the test was 93.3% (95%CI 88.1-96.8) at 6 h post INH, 93.4% (95%CI 88.2-96.8) at 12 h and 77% (95%CI 69.1-83.7) at 24 h. The specificity of the test was 98.3% (95%CI 91.1->99.9). There was no association between smoking status and colour change of positive results.


CONCLUSIONS
This test is a useful method of monitoring adherence to TB treatment or preventive therapy among South Africans. However, it is less than 100% sensitive, especially with increasing time post dose, which should be taken into consideration when interpreting results for individual patients.
Hanifa
Y
Y
Aurum Institute for Health Research, Johannesburg, South Africa; Centre for the AIDS Programme of Research in South Africa (CAPRISA), University of KwaZulu-Natal, Durban, South Africa. yhanifa@auruminstitute.org
Mngadi
K
K
Lewis
J
J
Fielding
K
K
Churchyard
G
G
Grant
A D
AD
D000328:Adult; D000995:Antitubercular Agents / Q000008:administration & dosage / Q000627:therapeutic use / Q000652:urine*; D003430:Cross-Sectional Studies; D006801:Humans; D007538:Isoniazid / Q000652:urine*; D008297:Male; D008875:Middle Aged; D010349:Patient Compliance; D012680:Sensitivity and Specificity; D012907:Smoking; D013019:South Africa; D014376:Tuberculosis / Q000188:drug therapy*
D000995:Antitubercular Agents; D007538:Isoniazid