Chemical Examination of Urine Flashcards
Products of fat metabolism (ketones)
Acetate (2%)
Acetoacetic acid (20%)
beta-hydroxybutyric acid (78%)
Reagent Strip for Ketones
Sodium nitroprusside (purple)
Acetest
Tablet test for ketones; Sodium nitroprusside Glycine Disodium phosphate Lactose
Produce an interfering red colour in alkaline test medium for ketones
Phenolsulfonphthalein
Bromsulphalein
Hematuria
Cloudy red urine
Renal or GUT origin
Cause: Trauma
Renal Calculi
Glomerular diseases
Tumors
Pyelonephritis
Anti-coagulant therapyHemoglobinuria
Clear red urine
Dilute alkaline urine
Intravascular hemolysis
Causes: Hemolytic anemia
HTR
Severe burns
Brown recluse spider bites
Infections
Strenuous exercise
Red plasmaLarge yellow-brown granules of denatured ferritin
hemosiderin
Myoglobinuria
Clear red-brown urine
Causes: Muscle destruction (Rhabdomyolysis)
Alcoholism
Heroin abuse
Elevated CK, LD
Normal colour on plasmaReagent strip reaction on blood
Pseudoperoxidase activity of haemoglobin
H2O2 + tetramethylbenzidine = green blue
False Positive Reactions (Blood)
Menstrual contamination
Strong oxidizing detergents
Vegetable peroxidase
Bacterial enzymes (E. coli)
False Negative Reactions (Blood)
Ascorbic acid High sp gr. Formalin Hypertension medication (Captopril) High concentrations of nitrite Failure to mix specimen
Multistix (blood)
uses peroxide less subject to reduction by ascorbic acid
Chemstrip (blood)
overlays the reagent pad with an iodate-impregnated mesh that oxidises ascorbic acid.
Bilirubin
Highly pigmented yellow compound
Degradation product of hemoglobin
Reagent strip reaction on bilirubin
Diazo reaction 2,4-dichloroaniline diazonium salt 2,6-dichlorobenzene-diazonium-tetrafluoroborate Acidic medium tan to violet
Ictotest
Bilirubin p-nitrobenzene-diazonium-p-toluenesulfonate SSA sodium carbonate boric acid blue to purple
False Positive Reactions (Bilirubin)
Urine pigments
Phenazopyridine
indican
metabolites of Lodine
False Negative Reactions (Blood)
Not fresh specimen photo-oxidized bilirubin hydrolysis of bilirubin diglucoronide ascorbic acid nitrite
Urobilin
brown color of feces
Multistix (urobilinogen)
Ehrlich’s aldehyde reaction
p-dimethylaminobenzaldehyde
light to dark pink
Chemstrip (urobilinogen)
azo-coupling (diazo reaction)
4-methoxybenzene-diazonium-tetrafluroborate
white to pink
False Positive Reactions (Urobilinogen)
Ehrlich-reactive compounds pophobilinogen indican p-aminosalicylic acid sulfonamides methly dopa procaine chlorpromazine heavy meal
False Negative Reactions (Urobilinogen)
improperly preserved
nitrite
formalin
Watson-Schwartz Differentiation Test
Urobilinogen is soluble in chloroform and butanol
Hoesch test
rapid screening or monitoring of urinary porphobilinogen Hoesch reagent (Ehrlich reagent dissolved in 6 M HCL)
Nitrite
UTI
Bladder infection (cystitis)
pyelonephritis
Greiss reaction
Nitrite
acidic pH
p-arsanilic acid / sulphanilamide -> diazonium compound (tetrahydrobenzoquinolin)
pink
False Negative Reactions (Nitrite)
Large number of bacteria (further reduction of nitrite to nitrogen)
Antibiotics
ascorbic acid
high sp gr
LE test
detect presence of WBCs that have been lysed
dilute alkaline urine
Indicators of UTI
Longest time of all reagent strip reactions
False Negative Reactions (LE)
protein
glucose
oxalic acid
ascorbic acid
