CE FDA 3 parameters Leukocytes Nitrite pH Urine test strips;
Glucose: This test is based on the enzymatic reaction that occurs between glucose oxidase, peroxidase and chromogen. Glucose is first oxidized to produce gluconic acid and hydrogen peroxide in the presence of glucose oxidase. The hydrogen peroxide reacts with potassium iodide chromogen in the presence of peroxidase. The extent to which the chromogen is oxidized determines the color which is produced, ranging from green to brown. Glucose should not be detected in normal urine. Small amounts of glucose maybe excreted by the kidney. Glucose concentrations as low as 5 mmol/ L maybe considered abnormal if results are consistent.
pH: This test is based on a double indicator system which gives a broad range of colors covering the entire urinary pH range. Colors range from orange to yellow and green to blue. The expected range for normal urine specimens from newborns is ph 5-7. The expected range for other normal urine specimen is pH 4.5-8, with an average result of ph 6.
Protein: This reaction is based on the phenomenon known as the “ protein error” of pH indicators where an indicator that is highly buffered will change color in the presence of proteins (anions) as the indicator releases hydrogen ions to the protein. At a constant pH, the development of any green color is due to the presence of protein. A color matching any block greater than trace indicates significant proteinuria. Clincal judgment is required to evaluate the significance of trace results.
Ketone: This test is based on ketones reacting with nitroprusside and acetoacetic acid to produce a color change ranging from light pinkfor negative results to a darker pink or purple color for positive results. Ketones are normally not present in urine. Detectable ketone levels may occur in urine during physiological stress conditions such as fasting, pregnancy and frequent strenuous exercise. In starvation diets, or in other abnormal carbohydrate metabolism situations, ketones appear in the urine in excessively high concentration before serum ketones are elevated.
Nitrites : may be a sign of urinary tract infection or other infection
Blood: This test is based on the peroxidase-like activity of hemoglobin which cartalyzes the reaction of diissopropylbenzene dihydroperoxide. The resulting color ranges from orange to green to dark blue. Any green spots or green color development on the reagent area within 60 seconds is significant and the urine specimen should be examined furthere, blood is often but not invariably. Found in the urine of menstruating females. The significance of a trace reading varies amoung patients and clinical judgement is required in these specimens.
Visual Reading Steps
Remove a test strip, taking care not to touch the reaction fields.
Immediately close the container again.
Dip the test strip for about 1-2 second into the fresh urine specimen.
Read the result by comparing the test fields with the color scale on the test pack after 40 seconds.