Lecture 2/16

• Leukocytes

  • indication of UTI
  • enzymatic reagent pad reaction
  • esterases present in granulocytes - looking for segmented neutrophils
• Macroscopic analysis

  • blood
  • potentially significant in any quantity
  • reagent pad detects 3 types
  • RBC (hematuria) - intact RBCs
  • hemoglobin - free; occurs when red blood cells hemolyze; aka hemoglobinuria
  • myoglobin - oxygen carrying pigment found in muscle
• positive blood dipstick is not specific to specific type

  trace amounts of blood may not change color of dipstick
• Macroscopic analysis

  • hematuria
  • pathological: renal calculi (kidney stones), glomerulonephritis, pyelonephritis, tumors, trauma, exposure to toxic chemicals/drugs
• 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