Urinalysis: Specific Gravity Calculation
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Urinalysis: Specific Gravity Calculation

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Questions and Answers

What is the correction factor for glucose in specific gravity measurement?

  • 0.003 for every g/dL glucose
  • 0.005 for every g/dL glucose
  • 0.004 for every g/dL glucose (correct)
  • 0.001 for every g/dL glucose
  • What is the purpose of the motion detector in the U-shaped glass tube?

  • To apply electric current to the coil
  • To amplify the electric current
  • To detect the sound wave frequency (correct)
  • To measure the velocity of the sound wave
  • What is the calibration temperature usually printed on the instrument?

  • 30°C
  • 25°C
  • 35°C
  • 20°C (correct)
  • How does the microprocessor convert the reading to specific gravity?

    <p>By converting the change in sound wave frequency</p> Signup and view all the answers

    What is the refractive index a comparison of?

    <p>The velocity of light in air and in the urine sample</p> Signup and view all the answers

    What is the correction factor for protein in specific gravity measurement?

    <p>0.003 for every g/dL protein</p> Signup and view all the answers

    What is the purpose of electric current in the U-shaped glass tube?

    <p>To generate a sound wave in the urine sample</p> Signup and view all the answers

    What is the correction factor for temperature in specific gravity measurement?

    <p>Deduct 0.001 for every 3°C above the calibration temperature</p> Signup and view all the answers

    Which of the following is the purpose of cytodiagnostic urine testing?

    <p>To provide definitive information about renal tubular changes associated with transplant rejection</p> Signup and view all the answers

    Why is it recommended to use reduced light when examining unstained sediment by bright-field microscope?

    <p>To reduce glare from the microscope</p> Signup and view all the answers

    What is the purpose of reporting the microscopic examination of urine?

    <p>To provide consistent results within a laboratory system</p> Signup and view all the answers

    What type of stain is used for slides prepared by cytocentrifugation?

    <p>Papanicolaou stain</p> Signup and view all the answers

    What is the first step in the formation of bilirubin?

    <p>Hemoglobin breakdown into heme</p> Signup and view all the answers

    What is the purpose of scanning the cover-slip perimeter under LPO?

    <p>To examine hemosiderin-containing cells and casts</p> Signup and view all the answers

    What is the role of the urinalysis laboratory in cases with unusual cellular findings?

    <p>To refer specimens to the cytology laboratory for further examination</p> Signup and view all the answers

    What is the role of glucoronic acid in bilirubin formation?

    <p>Conjugation with bilirubin</p> Signup and view all the answers

    What is the purpose of converting the number of elements per LPF or HPF to the number per mL?

    <p>To provide standardization</p> Signup and view all the answers

    What is the purpose of the reagent peroxide in the blood reagent strip?

    <p>To oxidize the chromogen</p> Signup and view all the answers

    What is the clinical significance of conjugated bilirubin in the urine?

    <p>It is an indicator of liver disease</p> Signup and view all the answers

    What is the term used to describe the number of RBCs and WBCs observed under the microscope?

    <p>Semiquantitative terms</p> Signup and view all the answers

    What is the purpose of the reagent tetramethylbenzidine in the blood reagent strip?

    <p>To act as a chromogen</p> Signup and view all the answers

    What is the result of bilirubin formation in the intestines?

    <p>Formation of urobilinogen</p> Signup and view all the answers

    What is the significance of bilirubinuria in liver disease?

    <p>It is an early indicator of liver disease</p> Signup and view all the answers

    What is the result of intact RBCs on the pad in the blood reagent strip?

    <p>Formation of a speckled pattern</p> Signup and view all the answers

    What is the primary function of the oculars/eyepiece lens?

    <p>To further magnify and concentrate light into the specimen</p> Signup and view all the answers

    What is the purpose of the Abbe condenser?

    <p>To optimize light quality and sharpness</p> Signup and view all the answers

    What is the function of the iris diaphragm?

    <p>To control the amount of light passing through the specimen</p> Signup and view all the answers

    What is the purpose of the field diaphragm?

    <p>To focus the light onto the stage</p> Signup and view all the answers

    What is the main purpose of Kohler illumination?

    <p>To optimize light quality and sharpness</p> Signup and view all the answers

    What happens to the image in the microscope?

    <p>It appears upside down and reversed</p> Signup and view all the answers

    When is Kohler illumination performed?

    <p>Whenever an objective is changed</p> Signup and view all the answers

    What is the purpose of the objectives in the lens system?

    <p>To perform the initial magnification</p> Signup and view all the answers

    What is the purpose of adding 0.005 to specific gravity readings when the pH is 6.5 or higher?

    <p>To correct for the automated strip reader's error</p> Signup and view all the answers

    What is the reagent used in urine tests for ascorbic acid?

    <p>Methylene green</p> Signup and view all the answers

    What is the minimum amount of ascorbic acid detectable by C-Stix at 60 seconds?

    <p>25 mg/dL</p> Signup and view all the answers

    What is the significance of a urine test showing 150 mg/dL of ascorbic acid?

    <p>Adequate ascorbic acid therapy</p> Signup and view all the answers

    What is the purpose of microscopic examination of urine?

    <p>To identify and quantify insoluble materials in urine</p> Signup and view all the answers

    What is the significance of a urine test showing a color change from blue to purple?

    <p>Presence of ascorbic acid</p> Signup and view all the answers

    What is the role of neutral red in urine tests for ascorbic acid?

    <p>It provides a background color</p> Signup and view all the answers

    What is the correlation between the clarity of urine and the presence of hematuria?

    <p>Cloudy urine indicates the presence of hematuria</p> Signup and view all the answers

    Study Notes

    Urinalysis

    • Specific gravity measures the ability of the kidneys to reabsorb essential chemicals and water.
    • For every g/dL of CHON, deduct 0.003 from the specific gravity reading.
    • For every g/dL of glucose, deduct 0.004 from the specific gravity reading.
    • For every 3°C drop in calibration temperature, deduct 0.001 from the specific gravity reading.
    • For every 3°C above the calibration temperature, add 0.001 to the specific gravity reading.
    • Calibration temperature is usually 20°C.

    Clinical Microscopy

    • Refractometry measures specific gravity by measuring the refractive index.
    • Refractive index is a comparison of the velocity of sound waves in air and in the urine sample.
    • Electric current is applied to the coil, causing a sound wave to pass through the urine sample.
    • The microprocessor measures the change in sound wave frequency and converts it to specific gravity.

    Blood Reagent Strip

    • Pseudoperoxidase activity of hemoglobin is the principle of the blood reagent strip.
    • Reagents used are peroxide, tetramethylbenzidine, and buffer.
    • Reaction: H2O2 + chromogen –Hgb Peroxidase→ oxidized chromogen (yellow to green to blue color*) + H2O.
    • Sensitivity: Multistix (5-20 RBCs/mL, 0.015-0.062 mg/dL hgb), Chemstrip (5 RBCs/mL, hgb corresponding to 10 RBCs/mL).
    • Correlation with other tests: protein, microscopic examination.

    Bilirubin

    • Formation of bilirubin: RES (RBC → hgb → heme → protoporphyrin → biliverdin → B1) → circulation (B1 coupled with albumin) → liver (B1 conjugated with glucoronic acid to form B2) → intestines (B2 converted to urobilinogen by intestinal bacteria).
    • Clinical significance of bilirubinuria: early indicator of liver disease, conjugated bilirubin appears in urine when there is bile duct obstruction or liver damage.
    • Used in determining the cause of jaundice.

    Ascorbic Acid

    • Urine tests for ascorbic acid have been used as an indication of adequate ascorbic acid therapy.
    • Large quantities of ascorbic acid may occasionally be found in the urine of individuals taking therapeutic doses of vitamin C or other preparations containing ascorbic acid.
    • Reagent: methylene green, which is reduced to its colorless form with ascorbic acid.
    • Neutral red provides a background color, and the overall color changes from blue to purple at levels of 150 mg/dL.

    Microscopic Examination of Urine

    • Used to detect and identify insoluble materials in urine.
    • Must include quantitation of elements present.
    • Some elements are considered normal unless present in increased amounts.
    • Slide examined first under LPO, setting changed to HPO for identification.
    • LPO scanning of cover-slip perimeter is recommended.
    • For detection of casts, use reduced light when examining unstained sediment by bright-field microscope.

    Reporting the Microscopic Examination

    • May vary among laboratories but must be consistent within a particular laboratory system.
    • Routine reporting includes:
      • Casts: per 10 LPFs.
      • RBCs and WBCs: per 10 HPFs.
      • Epithelial cells, crystals, and other elements: semi-quantitative terms (rare, few, moderate, many).

    Oculars/Eyepiece Lens

    • Responsible for further magnification and resolution (ability to visualize fine details).
    • Coarse- and fine-adjustment knobs.
    • Iris diaphragm: controls the amount of light that will pass through the specimen.
    • Rheostat: controls the intensity of light.
    • Image in the microscope is upside down and reversed.

    Microscopy

    • Kohler illumination is a technique to optimize light quality and sharpness by aligning and adjusting each component of the optical system.
    • Adjustments done to provide optimal viewing of illuminated objects.
    • Steps:
      • Place a slide on the stage and focus using LPO with the condensers raised.
      • ...

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    Description

    This quiz covers the calculations involved in determining specific gravity in urinalysis, including the effects of glucose and temperature on specific gravity measurements.

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