Urinalysis and Body Fluids PDF

Urinalysis and Body Fluids URINALYSIS- CHEMICAL ANALYSIS AND INTERPRETATION Lecture 6  Reagent Strip Testing for Glucose Because of its value in the detection of diabetes mellitus, the glucose test is the most frequent test performed on urine. Early...

Urinalysis and Body Fluids URINALYSIS- CHEMICAL ANALYSIS AND INTERPRETATION Lecture 6  Reagent Strip Testing for Glucose Because of its value in the detection of diabetes mellitus, the glucose test is the most frequent test performed on urine. Early diagnosis of diabetes mellitus through blood and urine glucose tests provides a greatly improved prognosis.  Clinical Significance of Glucose Test on Urine Sample When the blood glucose level becomes very high (hyperglycemia), as occurs in diabetes mellitus, the tubular transport of glucose stops, and glucose appears in the urine. The blood level at which tubular re- absorption of Glucose stops (renal threshold) is approximately 160 – 180 mg/dL.  Reagent Strip Testing for Glucose Two very different tests have been used by laboratories to measure urinary glucose. Glucose Oxidase Procedure provides a specific test for glucose Copper Reduction Test is a general test for glucose and other reducing substances  Glucose Oxidase Procedure First step: glucose oxidase catalyzes a reaction between glucose and room air to produce gluconic acid and peroxide. (reduced) (oxidized) Second step: peroxidase catalyzes the reaction between peroxide and chromogen to form an oxidized colored compound that represents the presence of glucose.  Copper Reduction Test This test relies on the ability of glucose to reduce copper (II) sulfate to cuprous (I) oxide in the presence of alkali and heat. A color change progressing from a negative blue (CuSO4) through green, yellow, and orange/red (Cu2O) occurs when the reaction takes place. False Positive are patients without the disease who are incorrectly classified by the test as having the disease False Negative are patients with the disease who are incorrectly classified by the test to be disease-free  Reagent Strip Testing for Ketones Testing for urinary ketones is most valuable in the management and monitoring of insulin-dependent (type 1) diabetes mellitus. Ketonuria shows a deficiency in insulin, indicating the need to regulate dosage. Ketonuria is an early indicator of insufficient insulin production in type 1 diabetes and in patients with diabetes who experience medical problems in addition to diabetes. Reagent Strip Reactions for Ketones Reagent strip tests use the sodium nitroprusside (nitroferricyanide) reaction to measure ketones. In this reaction, acetoacetic acid reacts with sodium nitroprusside to produce a purple color. This test does not measure beta- hydroxybutyric acid and is only slightly sensitive to acetone when glycine is also present. Three types of Ketones present in Urine  Reagent Strip Testing for Blood Blood may be present in the urine either in the form of intact red blood cells (hematuria) or as the product of red blood cell destruction (hemoglobinuria). Blood present in large quantities can be detected visually. Hematuria produces a cloudy red urine, and hemoglobinuria appears as a clear red sample. Reagent Strip Testing for Bilirubin Appearance of bilirubin in the urine can provide an early indication of liver disease. Hepatitis and cirrhosis are common examples of conditions that produce liver damage, resulting in bilirubinuria. Detection of urinary bilirubin provide an early indication of liver disease. The presence or absence of urinary bilirubin can be used in determining the cause of clinical jaundice. Jaundice of the skin caused by buildup of Bilirubin.  Reagent Strip Testing for Urobilinogen A small amount of Urobilinogen— less than 1 mg/dL is normally found in the urine. Urobilin is the pigment responsible for the characteristic brown color of feces. Urobilinogen appears in the urine because, as it circulates in the blood en route to the liver, it passes through the kidney and is filtered by the glomerulus.