Routine Urinalysis PDF

Chemical Examination of Urine REAGENT STRIP  11-12 cm long  4-6 mm wide  With absorbent pad CARE OF REAGENT STRIPS  Store with dessicant in an opaque, tightly closed container.  Store below 30°C; do not freeze.  Do not expose to volatile fumes.  Do not use past the expiration date.  Do not...

Chemical Examination of Urine REAGENT STRIP  11-12 cm long  4-6 mm wide  With absorbent pad CARE OF REAGENT STRIPS  Store with dessicant in an opaque, tightly closed container.  Store below 30°C; do not freeze.  Do not expose to volatile fumes.  Do not use past the expiration date.  Do not use if chemical pads become discolored.  Remove strips immediately prior to use. REAGENT STRIP TECHNIQUE  Dip the reagent strip briefly (no longer than 1 second) into a well-mixed uncentrifuged urine specimen at room temperature.  Remove excess urine by touching the edge of the strip to the container as the strip is withdrawn.  Blot the edge of the strip on a disposable absorbent pad.  Wait the specified amount of time for the reaction to occur.  Compare the color reaction of the strip pads to the manufacturer’s color in good lighting. Automated Reagent Strip Readers “Reflectance Photometry” GLUCOSE  Principle: “Double Sequential Enzyme Reaction” GLUCOSE  Color Indicator: Glucose Oxidase and Peroxidase  Positive Color: Green to brown  Reagents: Multistix: Glucose oxidase, Peroxidase, Potassium iodide Chemstrip: Glucose oxidase, Peroxidase,Tetramethylbenzidine  False (+): Oxidizing agents, detergents  False (-): High levels of ascorbic acid, High levels of ketones, High specific gravity, Low temperatures, Improperly preserved specimens  Sensitivity: 100 mg/dL BILIRUBIN  Principle: “Diazo Reaction” BILIRUBIN  Color Indicator: Dichloroaniline  Positive Color: Tan or pink to violet  Reagents: Multistix: 2,4-dichloroaniline-diazonium salt Chemstrip: 2,6-dichlorobenzene-diazonium salt  False (+): Highly pigmented urines, phenazopyridine, Indican, Metabolites of Lodine  False (-): Specimen exposure to light, Ascorbic acid >25 mg/dL, High concentrations of nitrite KETONES  Principle: “Sodium Nitroprusside Reaction (Legal’s Test)” THREE FORMS OF KETONE BODIES 1. Acetone – less sensitive 2. Acetoacetic acid (diacetic acid) – most sensitive; parent ketone 3. Beta-hydroxybutyric acid – major ketone not detected in reagent strip KETONES  Color Indicator: Sodium Nitroprusside  Positive Color: Purple  Reagents: Sodium nitroprusside, Glycine (Chemstrip)  False (+): Phthalein dyes, Highly pigmented red urine, Levodopa, Medications containing free sulfhydryl groups  False (-): Improperly preserved specimens SPECIFIC GRAVITY  Principle: “pKa change of a polyelectrolyte” Blue [1.000]-------> Green -------> Yellow [1.030] (↓H) (↑H+) (↑↑↑ H+) SPECIFIC GRAVITY  Color Indicator: Bromthymol Blue  Positive Color: Blue (SG 1.000) to Yellow (SG 1.030)  Reagents: Multistix: Poly (methyl vinyl ether/maleic anhydride) bromthymol blue Chemstrip: Ethyleneglycoldiaminoethylethertetraacetic acid, bromthymol blue  False (+): High concentrations of protein  False (-): Highly alkaline urines (>6.5) BLOOD  Principle: “Pseudoperoxidase Activity of Hemoglobin” BLOOD  Color Indicator: Tetramethylbenzidine  Positive Color: Uniform green/blue (Hgb or Mb) Speckled/spotted (Intact RBCs)  Reagents: Multistix: Diisopropylbenzene dehydroperoxide tetramethylbenzidine Chemstrip: Dimethyldihydroperoxyhexane tetramethylbenzidine  False (+): Strong oxidizing agents, Bacterial peroxidases, Menstrual contamination  False (-): High specific gravity/crenated cells, Formalin, Captopril, High concentrations of nitrite, Ascorbic acid >25 mg/dL, Unmixed specimens pH  Principle: “Double Indicator System” pH  Color Indicator: Methyl Red and Bromthymol Blue  Positive Color: Orange (pH 5.0) to Blue (pH 9.0)  Reagents: Methyl red and bromthymol blue  No known interfering substances  Sources of error: Runover from adjacent pads, old specimen PROTEIN  Principle: “Protein Error of Indicators” PROTEIN  Color Indicator: Tetrabromphenol Blue  Positive Color: Blue  Reagents: Multistix: Tetrabromphenol blue Chemstrip: Tetrachlorophenol tetrabromosulfophthalein  False (+): Highly buffered alkaline urine, pigmented specimens, phenazopyridine, quaternary ammonium compounds (detergents), antiseptics, chlorhexidine, loss of buffer from prolonged exposure of the reagent strip to the specimen, high specific gravity  False (-): Proteins other than albumin, Microalbuminuria UROBILINOGEN  Principle: “Ehrlich Reaction” UROBILINOGEN  Color Indicator: PDAB (paradimethylaminobenzaldehyde)  Positive Color: Cherry Red  Reagents: Multistix: p-dimethylaminobenzaldehyde Chemstrip: 4-methoxybenzene-diazonium-tetrafluoroborate  False (+): Ehrlich-reactive compounds (methyldopa), highly pigmented urine  False (-): old specimens, preservation in formalin, high concentrations of nitrite NITRITE  Principle: “Griess Reaction” NITRITE  Color Indicator: Tetrahydrobenzoquinolin  Positive Color: Uniform pink  Reagents: Multistix: p-arsanilic acid Tetrahydrobenzo(h)-quinolin-3-ol Chemstrip: Sulfanilamide, hydroxytetrahydro benzoquinoline  False (+): Improperly preserved specimens, Highly pigmented urine  False (-): Nonreductase-containing bacteria, Insufficient contact time between bacteria and urinary nitrate, Lack of urinary nitrate, Large quantities of bacteria converting nitrite to nitrogen, Presence of antibiotics, High concentrations of ascorbic acid, High specific gravity LEUKOCYTE ESTERASE  Principle: “Leukocyte Esterase Reaction” LEUKOCYTE ESTERASE  Color Indicator: Diazonium Salt  Positive Color: Purple  Reagents: Multistix: Derivatized pyrrole amino acid ester, Diazonium salt Chemstrip: Indoxylcarbonic acid ester, Diazonium salt  False (+): Strong oxidizing agents, Formalin, Highly pigmented urine, nitrofurantoin  False (-): High concentrations of protein, glucose, oxalic acid, ascorbic acid, gentamicin, cephalosporins, tetracyclines, inaccurate timing ASCORBIC ACID  A reducing agent that causes false-negative reactions on: Blood Bilirubin Leukocyte Nitrite Glucose