CMT Laboratory Procedures and Specimen Collection 2 — Questions and Answers
Question 1: The preferred method for collecting a urine specimen for routine urinalysis and culture is:
- First-morning random void
- Midstream clean-catch (Correct answer)
- Catheterized specimen via suprapubic tap
- 24-hour collection
Correct answer: Midstream clean-catch
A midstream clean-catch specimen minimizes contamination from urethral flora by discarding the initial urine stream before collecting the mid-portion.
Question 2: A 24-hour urine collection should be stored at which condition during the collection period?
- Room temperature with no preservative
- Refrigerated at 2–8°C or with a specified preservative (Correct answer)
- Frozen at –20°C throughout collection
- Warmed to body temperature
Correct answer: Refrigerated at 2–8°C or with a specified preservative
Refrigeration at 2–8°C or use of the appropriate chemical preservative prevents bacterial growth and analyte degradation during the full 24-hour collection period.
Question 3: On a urine dipstick, a positive nitrite result suggests the presence of:
- Renal calculi
- Glucose in the urine
- Gram-negative bacterial infection (Correct answer)
- Blood in the urine
Correct answer: Gram-negative bacterial infection
Many gram-negative bacteria convert urinary nitrates to nitrites via bacterial reductase, making a positive nitrite test an indicator of gram-negative urinary tract infection.
Question 4: When collecting a stool specimen for occult blood testing, the patient should avoid which food for 3 days before collection?
- White rice
- Red meat and raw broccoli (Correct answer)
- White bread
- Low-fat dairy products
Correct answer: Red meat and raw broccoli
Red meat contains hemoglobin, and certain raw vegetables contain peroxidases, both of which can cause false-positive guaiac-based occult blood tests.
Question 5: Which technique is used to collect a throat culture for Group A Streptococcus?
- Swab the inner cheeks and gumline
- Swab the tonsils and posterior pharynx while avoiding the tongue and teeth (Correct answer)
- Insert the swab into the nasopharynx
- Swab the anterior nares bilaterally
Correct answer: Swab the tonsils and posterior pharynx while avoiding the tongue and teeth
Group A Strep colonizes the tonsils and posterior pharynx; swabbing there while avoiding contamination from saliva on the tongue and teeth yields the most accurate specimen.
Question 6: A sputum specimen for culture should ideally be collected:
- After a full meal to maximize secretions
- First thing in the morning before eating or brushing teeth (Correct answer)
- After vigorous exercise
- At bedtime following oral hygiene
Correct answer: First thing in the morning before eating or brushing teeth
First-morning sputum contains the highest concentration of overnight accumulated secretions from the lower respiratory tract, improving diagnostic yield.
Question 7: A wound culture specimen should be collected from which area of the wound for the most accurate results?
- The wound edge or surrounding skin
- The deepest cleanest tissue at the wound base after cleansing (Correct answer)
- The exudate on the wound surface before cleansing
- Multiple swabs of all necrotic tissue
Correct answer: The deepest cleanest tissue at the wound base after cleansing
Collecting from the deepest viable tissue after surface cleansing avoids surface contaminants and identifies the true causative organisms rather than colonizing bacteria.
CMT Laboratory Procedures and Specimen Collection 2
The preferred method for collecting a urine specimen for routine urinalysis and culture is: