▸ Protein test pad is based on the principle of ‘protein error of indicators’ in which tetrabromphenol blue is yellow at the pH of 3 in absence of proteinuria

▸ Change in colour correlates with the concentration of albumin, the main urinary protein the test is sensitive for

▸ Dipstick protein pad gives a semiquantitative result

▸ For accurate quantification of proteinuria, request timed urine collection or protein/creatine ratio

▸ The protein pad does not detect other proteins such as gamma-globulins or Bence Jones proteins

▸ The protein pad is affected by the pH and the concentration of the urine sample

▸ Hence, false positives can be caused by alkaline or concentrated urine and conversely, false negatives can be due to acidic or dilute urine and when the primary protein is not albumin2

▸ Blood test pad detects tetramethylbenzidine caused by peroxidase-like reaction of haemoglobin

▸ Spotted positivity indicates intact red blood cells

▸ Uniform positivity indicates free haemoglobin

▸ Very sensitive test, hence negative result virtually eliminates haematuria

▸ Falsely positive in presence of ascorbic acid (vitamin C) in the urine, elevated specific gravity, pH <5.1, proteinuria and treatment with captopril2

▸ Leucocyte test pad detects leucocyte esterase enzyme released from lysed leucocytes in the urine

▸ False-positive results commonly occur with contamination of urine by vaginal secretions, flushing of the prepuce etc

▸ Most uropathogenic bacteria elaborate the nitrate reductase enzyme that reduces nitrates normally present in the urine to nitrites, which is detected by the nitrite test pad

▸ Sensitive test detecting even 10–15 organisms per mL of urine

▸ A positive nitrite test only means presence of bacteriuria, which often can be asymptomatic