Advertisements
| TEST PRINCIPLE TIME | REAGENTS | FALSE (+) | FALSE (-) |
| Glucose (correlated with ketones) Double sequential enzyme reaction ENZYMES: Glucose oxidase Peroxidase 30 s | M – glucose oxidase, peroxidase, potassium iodide C – glucose oxidase, peroxidase, tetramethylbenzidine CHROMOGENS: O-toluidine (pink to purple) Potassium iodide (blue to brown) Aminopropryl-carbazol (yellow to orange-brown) Tetramethylbenzidine (yellow to green) | Contamination by oxidizing agents and detergents | High levels of ascorbic acid, ketones, specific gravity Low temperature Improperly preserved specimens |
| Ketones (correlated with glucose) Sodium nitroprusside reaction 40 s | M – sodium nitroprusside (acetoacetic acid) C – sodium nitroprusside + glycine (acetoacetic acid & acetone) | Phthalein dyes, highly pigmented red urine, levodopa Medications containing free sulfhydryl groups (MESNA) | Improperly preserved specimens |
| Specific Gravity pKa change of polyelectrolyte pKa = dissociation constant 45 s | M – poly (methy lvinyl ether/maleic anhydride) bromthymol blue C – ethyleneglycol-Bis (aminoethylether) bromthymol blue | High concentrations of proteins because of protein anions | Highly alkaline urines (>6.5) Add 0.005 to S.G. readings |
| pH (correlated with Nitrite, LE, microscopic) Double-indicator system 60 s | Methyl red Bromthymol blue | None | Runover from the adjacent CHON pad may lower pH |
| Protein (correlated with blood, nitrite, LE, microscopic) Protein error of indicators 60 s | M – tetrabromphenol blue C – tetrachloropenol tetrabromosulfonphthalein ACID BUFFER: Citrate | Highly buffered alkaline urine High specific gravity pigmented specimens, phenazopyridine quaternary ammonium compounds (detergents) antiseptics, chlorhexidine loss of buffer from prolonged exposure of reagent strip to the specimen | Proteins other than albumin |
| Blood (correlated with protein and microscopic) Pseudo-peroxidase activity of hemoglobin 60 s | M – diisopropylbenzenedehydroperoxide tetramethylbenzidine C – dimethyldihyroperoxide- tetramethylbenzidine spotted blue for intact RBCs uniform blue for Hb and myoglobin | Strong oxidizing agents, bacterial peroxidases menstrual contamination | High specific gravity/ crenated cells high concentration of nitrite formalin, captopril, ascorbic acid > 25mg/dl unmixed specimens |
| Bilirubin (correlated with urobilinogen) Diazo reaction 60 s | M – 2,4-dichloro-analine diazonium salt C -2,6-dichorobenzene-diazonium-tetrafluoroborate | Highly pigmented urines, phenazopyridine, indican metabolites of Lodine | Specimen exposure to light, ascorbic acid >25 mg/dL, high concentration of nitrite |
| Urobilinogen (correlated with bilirubin) Ehrlich’s reaction 60 s | M – para-dimethylaminobenzaldehyde C – 4-methoxybenzenediazonium-tetrafluroborate | M – Porphobilinogen, indican, p-aminosalicyclic acid, sulfonamides, methyldopa, procaine, chlorpromazine, highly pigmented urine C – highly pigmented urine | M – old specimens, preservation in formalin C – old specimens, preservation in formalin, high concentration of nitrite |
| Nitrite (correlated with protein, LE and microscopic) Greiss reaction 60 s | M – p-arsanilic acid Tetrahydrobenzo(h)-quinolin-3-ol C – Sulfanilamide, hydroxytetrahydro benzoquinoline | Improperly preserved specimens Highly pigmented urine | Nonreductase-containing bacteria insufficient contact between bacteria and urinary nitrate (should be 4 hours) lack of urinary nitrate, large quantities of bacteria converting nitrite to nitrogen, presence of antibiotics, high concentration of ascorbic acid high specific gravity |
| Leukocytes (correlated with protein, nitrite and microscopic) Leukocyte esterase 120 s | M – derivatized pyerole amino acid ester, diazonium salt C – indoxylcarbonic acid ester diazonium salt | Strong oxidizing agents, Formalin, highly pigmented urine, nitrofurantoin | High concentration of protein, glucose, oxalic acid, ascorbic acid, gentamicin, cephalosporins, tetracyclines |
Doc Krizza-Almond 