CNA CNA Medical Lab and Specimen Collection Skills 1 — Questions and Answers
Question 1: When collecting a clean-catch midstream urine specimen, what is the correct sequence of steps?
- Void first portion, collect midstream, then finish voiding into toilet (Correct answer)
- Collect the first portion of urine stream into the specimen cup
- Collect the entire voiding into the specimen cup
- Collect the last portion of urine stream into the specimen cup
Correct answer: Void first portion, collect midstream, then finish voiding into toilet
A clean-catch midstream urine specimen requires the patient to void the first portion into the toilet, collect the midstream urine into the cup, and then finish voiding into the toilet. This technique minimizes contamination from skin flora around the urethral opening.
The clean-catch midstream technique is designed to collect urine with minimal contamination. The first portion of urine washes bacteria from the urethra and perineal area. The midstream portion reflects bladder urine more accurately. The patient or CNA should first clean the perineal area with antiseptic wipes, then have the patient void the initial stream (about 1-2 ounces) into the toilet, redirect the stream into the sterile cup to collect 1-2 ounces, and then finish voiding into the toilet. This specimen is commonly used to diagnose urinary tract infections.
Question 2: A patient requires a 24-hour urine collection. What should the CNA do at the START of the collection period?
- Discard the patient's first voiding, then begin collecting all subsequent voidings (Correct answer)
- Collect the patient's first voiding into the 24-hour container
- Ask the patient to void, collect it, and note the start time
- Begin collecting urine at exactly midnight regardless of the patient's voiding schedule
Correct answer: Discard the patient's first voiding, then begin collecting all subsequent voidings
To begin a 24-hour urine collection, the patient voids and that first specimen is discarded. The collection clock starts at that point, and ALL subsequent urine for the next 24 hours is collected. This ensures a complete 24-hour measurement.
A 24-hour urine collection measures substances excreted by the kidneys over an entire day, such as creatinine, protein, or hormones. The process: (1) Note the start time when the patient first voids — discard this void. (2) Collect ALL urine for the next 24 hours into the large container, which may contain a preservative. (3) Keep the container refrigerated or on ice throughout the collection. (4) At exactly 24 hours after the start time, have the patient void one final time — this IS collected. (5) Send the container to the lab promptly. Missing any void or failing to refrigerate can invalidate the test.
Question 3: When collecting a urine specimen from a patient with an indwelling Foley catheter, where should the CNA obtain the sample?
- From the drainage port on the catheter tubing using a sterile syringe (Correct answer)
- By disconnecting the catheter from the drainage bag and draining into a cup
- Directly from the urine drainage bag
- By removing and reinserting the catheter
Correct answer: From the drainage port on the catheter tubing using a sterile syringe
Urine specimens from Foley catheters must be obtained from the designated sampling port on the catheter tubing using a sterile syringe and needle or needleless system. The drainage bag contains old, potentially contaminated urine and should never be used for specimens.
The correct method for obtaining a catheter urine specimen: (1) Clamp the tubing below the sampling port for 15-30 minutes to allow fresh urine to accumulate. (2) Clean the sampling port with an alcohol wipe and allow to dry. (3) Insert a sterile syringe into the port and aspirate the needed amount (usually 10-30 mL). (4) Transfer the urine into a sterile specimen container. (5) Label appropriately and send to the lab. Never collect from the drainage bag because this urine can be hours old and contaminated. Never disconnect the catheter-bag junction because this breaks the closed system and introduces infection risk.
Question 4: A patient needs a stool specimen for occult blood testing. What food should the patient avoid before this test?
- Red meat, raw vegetables, and aspirin (Correct answer)
- Dairy products and eggs
- Citrus fruits and juices
- Caffeinated beverages and chocolate
Correct answer: Red meat, raw vegetables, and aspirin
Before a fecal occult blood test (FOBT), patients should avoid red meat (contains blood), certain raw vegetables like radishes and turnips, vitamin C supplements, and aspirin/NSAIDs that can irritate the GI tract and cause false positives or negatives.
Fecal occult blood testing detects hidden (occult) blood in stool, which can be an early sign of colorectal cancer or other GI conditions. Dietary restrictions (typically 3 days before testing) include: Red meat (beef, lamb, pork) because hemoglobin can cause false positives; Raw turnips, radishes, broccoli, and cantaloupe contain peroxidase enzymes that mimic the test reaction; High doses of vitamin C can cause false negatives by blocking the chemical reaction; Aspirin and NSAIDs may cause GI irritation and minor bleeding. The CNA should educate patients about these restrictions and document patient understanding.
Question 5: When collecting a stool specimen, how much stool is typically required?
- About the size of a walnut (1-2 tablespoons) (Correct answer)
- An entire bowel movement
- Just a small smear on the collection card
- A full specimen cup
Correct answer: About the size of a walnut (1-2 tablespoons)
For most stool specimens, a walnut-sized amount (approximately 1-2 tablespoons) is sufficient. The exact amount may vary by test type, but this is the general guideline. For FOBT cards, a small smear from two different parts of the stool is used.
The amount of stool required varies by test type: (1) Culture or ova and parasite testing: about 1-2 tablespoons placed in a sterile container with or without preservative. (2) Fecal occult blood test (FOBT) cards: a thin smear from two separate areas of the stool applied to the card windows. (3) C. difficile testing: liquid or soft stool in a clean container, about 5-10 mL. Important collection rules: use the tongue blade or collection spoon provided, do not contaminate stool with urine or toilet water (use a specimen hat in the toilet), label the container with patient name/date/time, and send to lab promptly or refrigerate as instructed.
Question 6: A patient needs a sputum specimen for culture. When is the best time to collect this specimen?
- First thing in the morning before eating or drinking (Correct answer)
- After the patient eats a large meal
- In the afternoon when the patient has been active
- At bedtime after the patient has been resting all day
Correct answer: First thing in the morning before eating or drinking
Sputum is best collected early in the morning upon waking, before eating or oral hygiene. Secretions pool in the lungs overnight, making it easier to produce a true sputum sample with the most concentrated bacteria.
Optimal sputum collection technique: (1) Collect early morning before eating, drinking, or brushing teeth to avoid diluting or contaminating the sample. (2) Have the patient rinse their mouth with plain water (NOT mouthwash which kills bacteria). (3) Instruct the patient to take several deep breaths and cough forcefully from deep in the lungs — NOT just spit saliva. (4) Collect at least 5-10 mL of sputum (not saliva) in a sterile container. (5) If the patient cannot produce sputum, try chest physiotherapy, nebulizer treatment, or nasotracheal suctioning as ordered. (6) Label immediately and transport to the lab within 2 hours or refrigerate. Proper sputum (not saliva) is thick, possibly discolored, and comes from deep airways.
CNA CNA Medical Lab and Specimen Collection Skills 1
When collecting a clean-catch midstream urine specimen, what is the correct sequence of steps?