CHEMICAL EXAMINATION OF URINE.pdf

CHEMICAL EXAMINATION OF URINE Positive Negative Small quantity of 1. SULFOSALICYLIC ANALYSIS glucose Cold precipitation using 3% SSA...

CHEMICAL EXAMINATION OF URINE Positive Negative Small quantity of 1. SULFOSALICYLIC ANALYSIS glucose Cold precipitation using 3% SSA Reacts equally with all form of protein REAGENT STRIPS METHOD Provide simple, rapid means for performing medically significant chemical analysis of urine Parameters used in the reagent strips: pH, protein, glucose, ketones, blood, bilirubin, urobilinogen, nitrite, leukocytes and specific gravity. Two major types of reagent strips: Multistix and chemstrip Quality control: reagent strips must be checked with positive and negative controls a minimum of once every 24 hours. Glucose 2.COPPER REDUCTION TEST (CLINITEST) almost all the glucose filtertered by the Test the ability of glucose to reduce copper glomerulus is actively reabsorbed in the sulfate, to cuprous oxidein the presence of PCT, therefore urine contains minute alkali and heat. amounts of glucose At high glucose level, Pass through phenomenon may occur. Color passes Principle: Double sequential enzyme reaction through the orange or red stage and returns to a green brown color, and if not observed, 1. Glucose+02—glucose oxidase—>Gluconic a high glucose level may be reposted as acid+H2O2 negative. To minimize this, use 2 drops instead of 5 drops of urine. 2. H2O2+ chromogen—Peroxidase—>Oxidized colored chromogen + H2O GLUCOSE COPPER INTERPRETATION OXIDASE REDUCTION Chromogen used: Positive Positive Glucose or glucose Potassium iodide (Green to brown) multistix plus other reducing tetramethylbenzidine (yellow to green) substances chemstrip Negative Positive Non-glucose Reporting: Negative,trace, 1+, 2+,3+,4+ /however reducing the color charts also provide quantitative substances or measurements. interference from Time frame: 30 seconds ascorbic acid  As the SG increases the indicator pad Renal False False Negative changes from blue (alkaline) to shades of threshold: positive: a. Ascorbic acid green to yellow (acidic) 160- 180 Oxidizing b. High SG False positive: High concentration of protein mg/dL agents c. Ketones False negative: High alkaline urine >6.5 Detergents d. Low temperatures e. Improperly Ketones preserved Intermediate product of fat metabolism specimens *acetone 2% ( chemstrip +glycine) *acetoacetic acid 20% ( detected by multistix) Bilirubin *beta-hydroxy butyrate 78% Time frame: 40 seconds Highly pigmented compound Principle: Sodium nitriprusside (nitroferricyanide Degradation product of hemoglobin reaction) Limitation: prolonged exposure of sample to light Acetoacetate (acetone)+ sodium nitroprusside *it only measures direct bilirubin (glycine) —alkaline—> purple color Principle: Diazo reaction (time frame: 30 seconds) Bilirubin glucuronide + diazonium salt–acid–> azodye Early False Positive False negative *Color ranging: increasing degrees of tan to pink indicator of a. Levadopa a.Improperly Ictotest: confirmatory test for bilirubin insufficient b.Sulfhydryl preserved insulin medication specimen Only False Positive: False dosage in c.Phthalein conjugated a. Pigmented negative: type 1 dyes bilirubin can specimen a. diabetes d.Pigmented appear in the b Phenazopyridine Exposure specimen urine c.Indican to light d.Lodine b Ascorbic Bilirubinuria acid >25 Blood in hepatitis mg/dL Pseudo peroxidase activity of hemoglobin cirrhosis c High Time Frame:60 seconds gallstones concentrati positive reagent strip indicates presence carcinoma on of nitrite hematuria), hemoglobin, myoglobin H2O2+ chromogen–Hemoglobin peroxidase—>Oxidized chromogen + H20 (green to Specific gravity blue) Chromogen used: tetramethylbenzidine Principle: Change in pKa of polyelectrolyte in Speckled pattern indicative of alkaline medium hematuria Time frame: 45 seconds the polyelectrolytes ionizes, releasing False positive False Negative hydrogen ions in proportion to the number a.Oxidizing agent a.Ascorbic acid>25mg/dL of ions in the solution. b.Bacterial b.High SG The higher the concentration of urine, the peroxidase c.Formalin more hydrogen ions are released, thereby c.Menstrual d.Crenated cells lowering the pH contamination e.Captopril f.High concentration of nitrite  g.Unmixed specimen Leukocyte esterase Principle:Leukocyte esterase reaction pH Time frame: 2 minutes Principle:Double indicator system of methyl red Can detect False positive False and bromthymol blue leukocytes that A.Formalin negative Time frame: 60 seconds have been b.Strong a. Ascorbic *4.5-8.0 pH of normal random samples lysed, oxidizing agent acid *>8.5 pH of improperly preserved sample especially in c.Highly b.Protein *False acidic reading in an alkaline urine due to dilute alkaline pigmented >500 mg/dL run over between pH and protein pads urine urine c.Glucose > d.Nitrofurantoin 3g/dL Protein Esterase are d.Oxalic acid Principle: Protein error of indicator also present in e.Antibiotic Note: presence of protein can alter the color of trichomonas f.Inaccurate indicator w/o changing the pH and histiocyte timing Normal: