Urinalysis & Body Fluids: Pre-Analytical Examination (p.381-p.383) Flashcards
Urinalysis: Pre-Analytical Examination (p.381)
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
{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 (p.413)}
Urinalysis: Pre-Analytical Examination (p.381)
False results in urobilinogen testing may occur if the urine specimen is:
a) exposed to light
b) adjusted to a neutral pH
c) cooled to room temperature
d) collected in a nonsterile container
a) exposed to light
{Urobilinogen is degraded by light. (p.413)}
Urinalysis: Pre-Analytical Examination (p.381)
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 is 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 microbiology department and urinalysis. Ideally, the culture is set up first to prevent contamination. If that is not feasible timewise, the sample should be aliquoted using aseptic technique, and refrigerated until it can be cultured. (p.413)}
Urinalysis: Pre-Analytical Examination (p.381)
Which of the following urine results is most apt to be changed by prolonged exposures to light?
a) pH
b) protein
c) ketones
d) bilirubin
d) bilirubin
{Bilirubin is degraded by light. The other analyses will not be affected. (p.413)}
Urinalysis: Pre-Analytical Examination (p.381)
Urine samples should be examined within 1 hour of voiding because:
a) RBCs, leukocytes and casts agglutinate on standing for several hours at room temperature
b) urobilinogen increases and bilirubin decreases after prolonged exposure to light
c) bacterial contamination will cause alkalization of the urine
d) ketones will increase due to bacterial and cellular metabolism
c) bacterial contamination will cause alkalization of the urine
{Evaluate each statement. a is incorrect because these cells don’t agglutinate. b is partially correct, but urobilinogen decreases in light. c is true, bacterial overgrowth does lead to an alkaline urine. d is false, ketones are produced by fat metabolism in the patient. (p.413}
Urinalysis: Pre-Analytical Examination (p.382)
The following results were obtained on a urine specimen at 8:00 am: pH: 5.5 protein: 2+ glucose: 3+ ketones: 3+ blood: negative bilirubin: positive nitrite: positive
If this urine specimen was stored uncapped at 5 °C without preservation and retested at 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. (p.413)}
Urinalysis: Pre-Analytical Examination (p.382)
A urine specimen comes to the laboratory 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 °C - 7 °C
c) frozen
d) with a preservation additive
b) at 4 °C - 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. (p.413)}
Urinalysis: Pre-Analytical Examination (p.382)
Which of the following would be affected by allowing a urine specimen to remain at room temperature for 3 hours before analysis?
a) occult blood
b) specific gravity
c) pH
d) protein
c) pH
{Consider whether a substance can increase or decrease outside the body. No more blood can be produced. Although the RBC may rupture, they will still make a positive result on a biochemical strip. The amount of solutes won’t change, so specific gravity won’t change. pH is affected by metabolism of urine components by bacteria, and room temperature is warm enough for this to occur. Protein will not increase or decrease. (p.413)}
Urinalysis: Pre-Analytical Examination (p.382)
A 24-hour urine from a man who had no evidence of kidney impairment was sent to the laboratory for hormone determination. The volume of 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 is <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 is > 1 g, do the procedure
d) check the creatinine level; if it is > 1 g, do the procedure
{The reader should know the approximate volume of a daily void, which is approximately 1,500 mL, but can range from 600-2,000 mL. In order to determine if 600 is the actual volume, or some sample was missed, evaluate the creatinine. Creatinine is excreted at approximately 1.2 mg/24 hours. Now evaluate the choices. a could be correct, but it is not sufficient, since 600 mL in unusually low. b is incorrect, because the creatinine is too low. c is incorrect, because it does not answer the medical question and it bills the patient. This leaves d, which is the correct answer. (p.413)}
Urinalysis: Pre-Analytical Examination (p.382)
Failure to observe RBC casts in a urine specimen can be because 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 of the specimen container. Without prior mixing, the sediment in the container may not be poured into the centrifuge tube. (p.413)}
Urinalysis: Pre-Analytical Examination (p.382)
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
{Several methods have been described to estimate glomerular filtration. The creatinine clearance test uses plasma creatinine vs. urine creatinine. However, it is unwieldy and time consuming for the patient. The new estimated formula, called the modification of diet in renal disease (MDRD) uses ethnicity, serum creatinine, BUN and serum albumin. (p.413)}
Urinalysis: Pre-Analytical Examination (p.382)
The creatinine clearance is reported in:
a) mg/dL
b) mg/24 hours
c) mL/min
d) mL/24 hours
c) mL/min
The creatinine clearance is a filtration rate, and is reported in minutes. The sample is a 24-hour urine, which is entered into the calculation as the volume in milliliters, and the factor of 1,440 minutes per 24 hours is applied. (p.413)}
Urinalysis: Pre-Analytical Examination (p.383)
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 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. (p.414)}
