nonpathological causes of hematuria - strenuous exercise, menstrual contamination
pH indications of hematuria
alkaline pH will lyse intact RBCs
delay in testing can lyse RBCs as pH increases
upon microscopic examination of alkaline urine, will not see intact RBCs or see ghost red cells (membrane very faint; Hgb leaked out of RBC and RBC filled with water or urine)
Macroscopic analysis - blood
hemoglobinuria - lysis of red cells in urinary tract or in alkaline urine
if hemoglobin pad is negative, myoglobin will be negative
therefore, if you receive myoglobin urine test, first do blood dipstick and if negative, do no further testing
methods of testing for blood - electrophoresis, adsorption spectrophotometry, immunodiffusion, and radioimmunoassays (historically)
macroscopic analysis - blood
reagent pad reaction uses pseudoperoxidase activity of Hgb
In reagent pad reaction for blood, sample provides peroxidase, while in glucose, reagent has peroxidase
Reaction interference of blood reagent pad
false positives with vegetable peroxidases - some vegetables have increased peroxidase
biliary obstruction can mean duct from gallbladder to liver or or liver to small intestine is blocked
macroscopic analysis - bilirubin
properties
normally negative
bilirubin in urine will always be conjugated
breaks down in light
macroscopic analysis - urobilinogen
source - degradation of hemoglobin; 1 mg/dL is normal; varies; levels rise 2-3 hours after a meal
chemstrip for urobilinogen - has different chemical
positive is pink to red
macroscopic analysis - nitrite
background - normal diet with green vegetables results in nitrate in the urine; some bacteria reduce nitrate to nitrite (NO2); other bacteria reduce all the way to nitrogen (N2)
macroscopic analysis - nitrites
clinical significance - detects UTI's; positive indicates cystitis and pyelonephritis; evaluates effectiveness of antibiotic therapy
interferences of nitrite
false positive from pigmented urines
false negatives from bacteria that don't reduce nitrate, or reduce all the way to nitrogen
bacteria present, but will not be positive
false negative if diet is deficient from. nitrate rich foods
not enough nitrate to become nitrite
diluted specimens will give false negative
not enough contact time in bladder to convert nitrate to nitrite
Observances and Determinations -will not trigger microscopic
glucose - sometimes yes for microscopic evaluation to check if there is yeast infection especially in diabetics
microscopic analysis
can help differentiate UTI from renal disease
usually done on unstained "wet prep" - special chamber
having a special chamber for urine sediment analysis standardized amount of sediment examined
glitter cells result from brownian motion; before lysing, granules move around and WBC's appear to glitter