| Laboratory: | Clinical Microbiology |
| Test Name: |
MYCOBACTERIA (ACID-FAST BACILLI [AFB]), CULTURE, URINE
Test Code:
AFBF
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| Clinical Information: |
Test Indications:
Urine for AFB testing may be submitted for patients suspected of genitourinary tuberculosis. Urine AFB specimens should not be submitted for a routine screen; samples should only be submitted if renal or urinary tract tuberculosis is suspected. Recommendations: Current guidelines recommend that: A first-morning urine specimen is preferred. Replicate specimens should be limited to 1 per day for 3 days. The patients should be off fluoroquinolones for 48 hours prior to sample collection for AFB. The fluoroquinolones may affect the mycobacteria and reduce the mycobacterial culture yield. Shared Health Testing Process - Every AFB urine sample is evaluated by microscopy and culture. Smears are reported semi-quantitatively (Negative or 1+ to 4+). Cultures are incubated for 7 weeks and reported as soon as growth is detected. All microscopy smear positive AFB samples receive nucleic acid amplification testing (NAAT). AFB smear negative samples require a microbiologist consult if a NAAT is required. The in-house NAAT detects M. tuberculosis and Mycobacterium spp. DNA. M. tuberculosis are routinely referred to the National Reference Centre for Mycobacteriology-National Microbiology Laboratory (NRCM-NML) for susceptibility testing. Susceptibility testing for non-tuberculous mycobacteria may be requested by consultation with the Shared Health Microbiologist-on-call. Patient Preparation Instructions: Patients' sample collection should be conducted in accordance with Infection and Control Practices. The WRHA Acute Infection Prevention and Control Manual states that "when collecting specimens for suspected or active TB, specimens must be collected utilizing Airborne Precautions regardless of age". Accurate patient identification must be made prior to sample collection. Patient identification should be done in accordance with site policy. Samples and requisitions must be labeled/completed in accordance with the Shared Health Specimen Acceptance Policy. Please indicate on the requisition if the patient has received intravesical Bacillus Calmette-Guerin therapy. Patient instructions for the collection of urine are available in Shared Health doc# PB120-10-05B. |
| Collection Devices: |
Preferred Device:
1 - Sterile Specimen Container (100 mL)
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| Specimen Required: |
40 mL of midstream urine or catheter urine, (minimum 10-15 mL) (Adult and Pediatric) For suprapubic taps, as much specimen as possible. Submit sample in a sterile container. Do not submit samples in a syringe with the needle attached. Do not pool urine samples. Do not add preservatives or additives. |
| Referral: |
Ensure samples that are being sent to a referral laboratory are packaged in accordance with Transport of Dangerous Goods recommendations for diagnostic samples.
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| Requisition: | |
| Reference Values: |
Microscopy: No acid-fast bacilli observed.
Culture: No acid fast bacilli isolated after 7 weeks of incubation. NAAT: Negative for Mycobacterium tuberculosis complex DNA and negative for Mycobacteria spp. DNA. |
| Availability: |
Weekdays
Weekdays (Monday - Friday). Mycobacteriology cultures are only performed at the Health Sciences Centre in Winnipeg. AFB positive smears of specimens are phoned to the nursing unit immediately. Culture positive index cases of M. tuberculosis are phoned to the nursing unit immediately. Positive M. tuberculosis NAAT results of index cases are phoned to the nursing unit immediately.
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| See Also: | |
| More Information: |
Specimen Handling:
Samples should be refrigerated for storage. |