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UW Health SMPH
American Family Children's Hospital

UW Hospital and Clinics Lab Test Directory

Test Name: AFB by PCR

Test Code(s): AFBPCR / HCAFBPCR

CPT Code(s): 87556

Clinical Significance: This test detects the M. tuberculosis complex.
This test is always performed on first smear positive specimens submitted to WSLH.

Testing Site: Testing will be sent to an approved reference laboratory.


Specimen Requirements

Specimen: See collection instructions.

Collection Instructions: Submit 3-10 mL of a primary respiratory specimen (sputum, tracheal aspirate, brochial washing, BAL).

For primary, non-respiratory specimens (body fluids, CSF, stool, urine, lung and other tissues):
Stool: 1 g in sterile container
Tissue Biopsy: 1 g in sterile container
Urine: 40 mL, first-morning, clean catch in sterile container (24-hour pooled specimen is unacceptable)
Body Fluids (pleural, pericardial, etc.): 5-10mL in sterile container
Whole Blood: 10 mL in SPS blood collection tube or Heparin tube (do not use EDTA)
Bone Marrow: As much as available in sterile container or SPS tube
CSF: As much as available in sterile container (minimum of 1 mL required)
Skin Lesions: scrapings or exudates; swabs are not recommended.  

Specimens with visible blood will be accepted. All specimens should be submitted in sterile, leak-proof containers.

Collection Container: Preferred: State Lab Acid Fast Bacillus (AFB) collection kit
Also Acceptable: Sterile screw cap container

Specimen Processing: TB PCR testing must be performed within 7 days of specimen collection.

Specimen Transport: Transport specimen to UWHC Core Laboratory (B4/220). Transport with coolant pack if coming from outreach location.

Unacceptable Criteria: Specimens from patients who have undergone antimicrobial therapy for TB for more than 7 days in the past 12 months.
Specimens from patients for whom suspicion of TB is low.

Stability: Refrigerated: 7 days
Frozen: Not acceptable


Interpretation

 

 

Test Limitations:

This tests detects M. tuberculosis complex but does not differentiate among its members.

Additional Information:

AFB smear and culture must also be ordered on any specimen submitted for PCR testing.

Mycobacteria

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