A comparison of screening tests for dapsone in urine

The comparative merits and limitations of three qualitative tests for Dapsone screening in urine viz. the 'Spot-Test' using modified Ehrlich's reagent, 'Tile-Test' employing Bratton-Marshall reagents, and the 'Elisa-Test' were assessed with regard to their sensitivity and operational feasibility. Investigations were carried out on a total of 716 urine specimens of which 268 specimens were collected during surprise visits paid to the patients homes. The others were specimens collected from patients at different time intervals following the administration of 25, 50 and 100 mg of dapsone. The findings were evaluated against their corresponding ratios of the urinary concentrations of Dapsone and its diazotisable metabolites to creatinine. A good correlation was found between the three qualitative tests in general and also in relation to the DDS/C ratios. Operational feasibility under field conditions for spot and tile tests are discussed.