Drug interference with urine protein determination

The purpose of this study was to detect the possibility of drug interference in the estimation of urine protein in patients receiving therapeutic doses of penicillin G, ampicillin, methicillin, cefoxitin, cefazolin, gentamicin, co-trimoxazole, phenothiazines, glibenclamide and acetazolamide. Five different methods for urine protein determination were compared in these patients, when different amounts of albumin were added to urine in vitro, and in a control group of patients not treated with drugs known to interfere with these methods. The techniques included two semi-quantitative tests--a strip test (Albustix) and heat and acetic acid turbidity test; and three quantitative tests--sulphosalicylic acid test, trichloroacetic acid test and a test based on a formation of Ponceau S dye-protein complex (Urin-Pak). The only significant interference found was that of gentamicin with the Ponceau S dye test.