lecture 2/9

• the glucose oxidase's chemical reaction can be described as a double sequential enzyme reaction
• deonzied/distilled water has a specific gravity of 1.000
• specific gravity examines the kidney's ability to concentrate urine
• HCG results on urine

  • if specific gravity is below 1.010, then HCG results may not be reliable, especially early in pregnancy
• there are no abnormal specific gravity values, just reflects the state of hydration or an issue with ADH
• diabetes insipidus causes a decrease in pH because of ADH abnormalities
• specific gravity methods

  • urinometer (hydrometer)
  • not generally used
  • requires too much specimen - ~5 mL
  • must be extremely careful when handling
• specific gravity - methods

  • refractometer
  • refractive index of light
  • advantages - requires only very small sample size, do not need temperature correction
  • disadvantages - only run 1 test at a time (labor intensive)
• refractometer

  • common usages - samples that have color interference on reagent strip (urines with puridium; amber colored urines [hemolytic rxns]; some urines with high bilirubin)
  • basically, if it's highly pigmented
• macroscopic analysis

  • specific gravity - methods
  • reagent strip - colorimetric estimation of ionic concentration; directly proportional to specific gravity
• pH strip monitors pH of 4.5 - 9.0 in increments of 0.5
• clinical significance of pH

  • helps determine respiratory/metabolic alkalosis/acidosis
  • helps detect in tubular reabsorption or secretion of acids or bases; helps ID crystals or enhance precipitation/formation of crystals
  • helps determine if specimen is appropriate -- urine will lever have a pH higher than 8.5
• macroscopic analysis

  protein - can be one of the earliest indicators of renal disease

  • as glomerulus is normally permeable to anything smaller than albumin; we can reabsorb small amounts if it gets through
  • in kidney disease, glomerulus becomes more permeable and gets in urine
  • microalbumin - more sensitive to proteinuria
• protein

  • normal values - negative
  • trace amounts may come from mucous or casts, as albumin gets stuck in casts/mucous and is not reabsorbed
  • must do microscopic analysis - see if there are casts, mucous, etc.; if none are present, not good for pt
• macroscopic analysis

  • sulfosalicylic acid precipitation
  • pick up any proteins in urine, broader spectrum
  • done on alkaline urines, depending on lab protocol
  • done one urines with color interference
• proteins

  macroscopic analysis - reagent has buffer and maintains steady pH on reagent pad
• clinitest (tablet into urine) uses the copper sulfate reaction
• other sources of protein in urine include

  • may come from seminal prostatic proteins in men
  • can contain vaginal proteins if contaminated
• protein reagent pad is based on errors of indicators