Pre-Analytical Examination Flashcards
After receiving a 24-hour urine for quantitative total protein analysis, the technician must first: A. subculture the urine for bacteria B. add the appropriate preservative C. screen for albumin using a dipstick D. measure the total volume
D. Measure the total volume of the sample before removing an aliquot. To calculate the total protein, measure the protein of an aliquot to learn the mg/dL. Then multiply that answer by the number of dL in the 24-hour collection.
False results in urobilinogen testing may occur if the urine specimen is: A. exposed to light B. adjusting to a neutral pH C. cooled to room temperature D. collected in a nonsterile container
A. Urobilinogen is degraded by light.
A clean-catch urine is submitted to the laboratory for routine urinalysis and culture. The routine urinalysis is done first and 3 hours later, the specimen is sent to the microbiology department for culture. The specimen should:
A. be centrifuged, and the supernatant cultured
B. be rejected due to the time delay
C. not be cultured if no bacteria are seen
D. be processed for culture only if the nitrate is positive
B- be rejected due to the time delay. It is common practice to share samples between the micro department and urinalysis. Ideally, the culture is set up first to prevent contamination. If that is not feasible time-wise, the sample should be aliquotted using aseptic technique, and refrigerated until it can be cultured.
Which of the following urine results is most apt to be changed by prolonged exposure to light? A. pH B. protein C. ketones D. bilirubin
D. Bilirubin is degraded by light. The other analytes will not be affected.
Urine samples should be examined within 1 hour of voiding because:
A. RBCs, leukocytes and casts agglutinate on standing for several hours at room temp
B. urobilinogen increases and bilirubin decreases after prolonged exposure to light
C. bacterial contamination will cause alkalinization of the urine
D. ketones will increase due to bacterial and cellular metabolism
C. Bacterial overgrowth does lead to an alkaline urine.
A is incorrect b/c these cells don’t agglutinate.
B is partially correct, but urobilinogen decreases in light.
D is false, ketones are produced by fat metabolism in the patient
The following results were obtained on a urine specimen at 8 AM: pH: 5.5 protein: 2+ glucose: 3+ ketones: 3+ blood: negative bilirubin: positive nitrite: positive If the urine specimen was stored uncapped at 5*C w/o preservation and retested a 2 PM, which of the following test results would be changed due to these storage conditions? A. glucose B. ketones C. protein D. nitrite
B- ketones. The sample is mistreated by being uncapped. It is refrigerated, which will prevent bacteria from reproducing (so D is incorrect), and from metabolizing glucose (so A is incorrect.) Ketones can evaporate, but protein will not.
A urine specimen comes to the lab 7 hours after it is obtained. It is acceptable for culture only if the specimen has been stored: A. at room temperature B. at 4* - 7* C C. frozen D. with a preservative additive
B- at 4* - 7* C. Storage must inhibit bacterial growth but not kill the bacteria. Freezing and additives are not acceptable. The most commonly used method of preservation is refrigeration.
Which of the following would be affected by allowing a urine specimen to remain at room temp for 3 hours before analysis? A. occult blood B. specific gravity C. pH D. protein
C- pH. pH is affected by metabolism of the urine components by bacteria, and room temp is warm enough for this to occur. Protein will not increase or decrease. The amount of solutes won’t change, so specific gravity won’t change. RBC’s may rupture, but they will sill make a positive result on a biochemical strip.
A 24-hour urine from a man who had no evidence of kidney impairment was sent to the lab for hormone determination. The volume was 600 mL, but there was some question as to the completeness of the 24-hour collection. The next step would be to:
A. perform the hormone determination, since 600 mL is a normal 24-hour urine volume
B. check the creatinine level; if it’s < 1 g, do the procedure
C. report the hormone determination in mg/dL in case the specimen was incomplete
D. check the creatinine level; if it > 1 g, do the procedure
D- check the creatinine level; if it > 1 g, do the procedure. Creatinine is excreted at approximately 1.2 mg/24 hour. The volume of a daily void can range from 600-2,000 mL
Failure to observe RBC casts in a urine specimen can be caused by:
A. staining the specimen
B. centrifuging an unmixed specimen
C. mixing the sediment after decantation
D. examining the sediment first under low power
B- centrifuging an unmixed specimen. Larger sediment constituents sink to the bottom. Without prior mixing, the sediment in the container may not be poured into the centrifuge tube.
eGFR calculated by the MDRD formula takes into account the age, BUN, race albumin, and what else for its calculations? A. urea B. ammonia C. creatinine D. cystatin C
C- creatinine. The MDRD (modification of diet in renal disease) uses ethnicity, serum creatinine, BUN and serum albumin.
The creatinine clearance is reported in: A. mg/dL B. mg/24 hours C. mL/min D. mL/24 hours
C- ml/min
Microalbumin can be measured by a random urine collection. An increased microalbumin is predictive of: A. diabetes mellitus B. nephropathy C. hypertension D. nephrotic syndrome
B- nephropathy. Patients with hypertension and diabetes mellitus are at risk for kidney disease. Detection of small amounts of albumin in the urine predict eventual kidney disease. The advantage of this sensitive detection is that patients with microalbuminuria can be treated with anti-hypertensive medications and followed up more intensely to delay nephropathy.
