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Routine chemical examination of the urine has changed dramatically since the early days of urine testing, owing to the development of the reagent strip method for chemical analysis. Reagent strips currently provide a simple, rapid means for performing 10 medically significant chemical analyses, including pH, protein, glucose, ketones, blood, bilirubin, urobilinogen, nitrite, leukocytes, and specific gravity.
Testing methodology consists of dipping the strip completely, but briefly, into a well-mixed urine specimen; removing excess urine by touching the edge of the strip to the container . Even though this is a simple procedure, improper technique can result in errors.
In addition to the use of correct testing technique, performance of quality control and care of reagent strips must be observed in order to guarantee quality patient care. All clinical laboratories must have a quality assurance program in place. Quality assurance program includes procedures for quality control of specimen collection and handling, reagents and test performance, instrument calibration and maintenance, reporting of results, personnel performance and requirements, safety, and documentation that the program is being followed.
Reagent strips must be protected from deterioration caused by moisture, volatile chemicals, heat, and light. Strips are packaged in opaque containers with desiccant, and when not in use, these bottles should be stored tightly closed in a cool area. Bottles should not be opened in the presence of volatile fumes. All bottles are stamped with an expiration date that represents the functional life expectancy of the chemical pads. This date must be honoured even if there is no noticeable deterioration of the reagents.
Unexpired strips should be tested for chemical reactivity with controls of known negative and abnormal concentrations. Distilled water is not recommended for use as a negative control because reagent strip chemical reactions are designed to perform at an ionic concentration consistent with urine. Additional or confirmatory procedures employing different chemical principles must be available for the substances being tested by reagent strip and should be used when questionable results are obtained or, in some instances, to confirm all positive results.
Observing all these procedures in routine urinalysis produces a win win situation between the laboratory and the patients. Our business is to provide a quality health care for our patients. But still, some laboratories do not comply with all these standards. An example of such violations is the cutting of reagent strips into halves.
To quote one of their reason, “We cut urine strips into halves since cut and whole strips will produce equal results, thus minimizing our costs and consequently the charge to our patients”.
I’m sure you are scratching your head right now. And if you happen to be the inspector, what would be your answer to this?
Reference: Susan King Strasinger: Urinalysis and body fluids.F.A. Davis Company, 1997
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