![]() Beta lactam antibiotics such as the penicillins, cephalosporins, carbapenems, and monobactams can cause false positive reactions. False positive reactions rarely occur, but may be produced by strong oxidizing cleaning agents. Urine should be at room temperature before the test is performed to obtain optimum sensitivity. High urine specific gravity can reduce color development. Urine specific gravity and temperature may affect test reactivity. The dipstick test is based on a double enzyme method employing glucose oxidase and peroxidase. The esterase reagent is sensitive to 15 leukocytes per hpf, but the protein reagent is sensitive to 6 leukocytes per hpf. Renal diseases are a common source of proteinuria.Īpproximately 25% of urine specimens containing bacteria will have a positive protein reaction as the only positive dipstick reaction. Hematologic malignancies, such as multiple myeloma, may produce excess immunoglobulin that is excreted in the urine. Strenuous exercise, fever, and exposure to extreme heat or cold, pregnancy, eclampsia, shock, and CHF cause functional proteinuria. Postural proteinuria occurs in 3 to 5% of healthy adults and is characterized by the presence of protein in the urine during the day but not the night. Confirmatory tests only need to be performed on those urine samples with positive protein and a pH of 7.5 or greater. Excessive contact with urine may wash out the buffering system and lead to a false positive result. False positive reactions can also be caused by contamination with quaternary ammonium compounds (zepharin, chlorhexidine) used to clean the skin for a clean catch urine. The major cause of a false positive urine protein is a highly alkaline sample. Dipsticks do not detect microalbuminuria.ĭipstick testing is useful only when urinary protein exceeds 300 to 500 mg/day or albumin exceeds 10 to 20 mg/day. Standard urine dipsticks are much less sensitive at detecting urine albumin than other assays. Dipsticks do not detect beta-2- microglobulin or immunoglobulin light chains. This test is optimized to detect albumin and is less sensitive in detecting globulins. Urine protein concentrations are reported as 30, 100, 300, or 2000 mg/dL. Dipsticks can detect protein concentrations as low as 5 to 30 mg/dL. The accuracy of this test depends on having urine that is slightly acidic. The color of positive reactions ranges from yellow-green to green to green-blue. The reagent pad contains the indicator and a buffer that holds the pH of the pad at approximately 3. tetrabromophenol blue) in the presence of varying concentrations of protein when the pH is held constant. The protein test is based on a change in color of a pH indicator (e.g. Pigmented urine can interfere with pH readings. Bacterial contaminants, blood in the urine and contamination by genital secretions can alter urine pH. Heavy bacterial growth may cause an alkaline shift in urine pH by converting urea to ammonia. A diet high in protein produces a more acid urine, while a vegetarian diet often produces a pH greater than 6. The average adult urine pH varies between 5 and 8. Metabolism produces acids that are excreted by the lungs and kidneys. ![]() The pH of urine is an indication of the kidney’s ability to maintain a normal plasma pH. pH should be measured in fresh urine and read quickly. Colors range from orange through yellow and green to blue. The test is based on a double indicator method (methyl red and bromthymol blue) that covers the entire range of urine pH. The principle and performance of each dipstick test is summarized below. Urine dipsticks are plastic strips with attached reagent pads for pH, protein, glucose, ketone, bilirubin, urobilinogen, blood, nitrite, and leukocyte esterase. However, most of the missed cases are clinically insignificant and are often due to contaminating bacteria multiplying after urine collection. Numerous studies have determined that 6 to 20% of patients with urine sediment abnormalities are missed by this testing strategy. Performing microscopic analysis on only dipstick positive urine samples is cost effective when the patient population being tested has a low incidence of potential disease. ![]() Urine samples are initially screened with dipsticks. Hematuria, hemoglobinuria, myoglobinuria, porphyriaīeets, blackberries, rhubarb, Phenolphthalein, rifampin Phenothiazines, phenazopyridine (Pyridium) Phosphorus, pyuria, chyluria, lipiduria, hyperoxaluriaĭiet high in purine-rich foods causing uricosuriaįava beans, Levodopa, metronidazole (Flagyl), nitrofurantoin, anti-malarial drugsĪmitriptyline, indigo, carmine, IV cimetidine (Tagamet), IV promethazine (Phenergan), methylene blue, triamterene (Dyrenium)
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