Activity 2.2
Chemical Examination of Urine:
Confirmatory Testing

Instructions

1. Practice the procedure for performing a chemical examination of urine following the step-by-step procedure.
   
   
2. Demonstrate your understanding of this lesson by:
   
   
• Completing a written examination successfully
  
  
• Performing the procedure for the chemical examination of urine satisfactorily for the instructor. All steps must be completed as listed.

Note: Consult reagent package inserts for manufacturers' specific instructions before performing tests.

Materials and Equipment

• Gloves
  
  
• Hand disinfectant
  
  
• Fresh urine samples
  
  
• Urine control solutions (normal and abnormal)
  
  
• Paper towels or laboratory tissues
  
  
• Stopwatch or timer
  
  
• Clear, conical graduated centrifuge tubes
  
  
• Forceps
  
  
• Centrifuge
  
  
• Heat-resistant test tubes, 13 × 100 mm and 16 × 125 mm
  
  
• Test tube clamp
  
  
• Dropping pipets
  
  
• Distilled water
  
  
• 20% sulfosalicylic acid (or 3%)
  
  
• Clinites tablets
  
  
• Acetes tablets
  
  
• Ictotes tablets and absorbent pads
  
  
• Test tube racks
  
  
• Worksheet
  
  
• Urinalysis report forms
  
  
• 10% chlorine bleach solution or other surface disinfectant
  
  
• Biohazard container
  
  
• Protective eyewear
  
  
• Puncture-proof sharps container
  
  

Procedure

1. Wash hands with disinfectant and put on gloves.
   
   
2. Assemble equipment and materials.
   
   
3. Obtain urine specimen and urine control solutions. If specimen has been refrigerated, allow it to reach room temperature before proceeding.

Sulfosalicylic Acid Test

• Perform sulfosalicylic acid test for protein (usually performed only if protein is positive by reagent strip method).
  
  
• Centrifuge 5 mL of urine.
  
  
• Place 4 mL of clear supernatant (from 5a) into a test tube.
  
  
• Add three drops of 20% sulfosalicylic acid (or add 4 mL of 3% sulfosalicylic acid).
  
  
• Mix thoroughly and estimate the amount of turbidity after ten minutes.
  
  
• Record results on worksheet as negative, trace, 1+, 2+, 3+, or 4+.

Clinitest

Perform Clinitest for reducing substances:

• Place a 16 × 125 mm test tube into a test-tube rack.
  
  
• Place five drops of urine into the test tube.
  
  
• Place ten drops of distilled water into the test tube.
  
  
• Drop a Clinitest reagent tablet into the urine-water mixture using forceps.
  
  
• Observe color while allowing tablet to effervesce or boil until boiling stops and without touching the test tube.
  
  
• Wait fifteen seconds, shake test tube gently using test tube clamp, and compare color to color chart. (The tube will be hot; the opening should be pointed away from your face.)
  
  
• Record results on worksheet as negative, 1/4%, 1/2%, 3/4%, 1%, or 2% or more.
  
  
• Repeat preceding steps using urine-control solution(s).

Acetest

Perform Acetest for ketones:

• Place an Acetest tablet on a clean piece of white paper towel or filter paper.
  
  
• Place one drop of urine on top of the tablet.
  
  
• Compare color of tablet to color chart at thirty seconds.
  
  
• Record results on worksheet as negative or positive.
  
  
• Repeat preceding using urine-control solution(s).

Ictotest

Perform Ictotest for bilirubin:

• Place ten drops of urine on an Ictotest mat.
  
  
• Place an Ictotest reagent tablet on the moistened area of the mat.
  
  
• Let two drops of water flow onto the tablet.

Note: When elevated amounts of bilirubin are present in the urine specimen, a blue to purple color forms on the mat within sixty seconds. The rapidity of the color formation and the color intensity are proportional to the amount of bilirubin in the urine. A pink or red color is a negative result.

• Record results on worksheet as negative or positive.
  
  
• Repeat preceding steps using urine-control solutions.