Nucleic Acid Amplification for M. tuberculosis complex

Laboratory Fee Schedule

Procedure #:  MAB0050A

CPT:  87556

Synonym(s): Direct Nucleic Acid Amplification Test (NAAT) for Mycobacterium tuberculosis complex, TB NAAT, NAA
Requisition Form G-MYCO
Test Description Nucleic Acid Amplification Testing of Clinical Specimens for detection of Mycobacterium tuberculosis complex and rifampin resistance.
Pre-Approval Needed For NAA testing of non-respiratory specimen types, please contact 512-776-7342.
Supplemental Information Required N/A
Supplemental Form(s) N/A
Performed on Specimens from (sources) Respiratory specimens from human.
Sample/Specimen Type for Testing
  • Sputum (unprocessed or processed sediment)  
  • bronchial washing (unprocessed or processed sediment)  
  • tracheal aspirates (unprocessed or processed sediment)  
Minimum Volume/Size Required 3 mL to 15 mL.
Storage/Preservation Prior to Shipping
  • Transport specimen as soon as possible. 
  • If transport is delayed over one hour, refrigerate specimen.
Transport Medium
  • Do not use transport medium.  
  • A sterile, leak-proof, 50 mL conical tube preferred for primary container.
Specimen Labeling
  • Two patient-specific identifiers required (e.g., patient full name, date of birth, medical record number)
  • Identifiers on specimen must exactly match submission form.
Shipping and Specimen Handling Requirements
  • Ship according to Dangerous Goods Regulations, IATA, and/or CFR 49
  • Category B shipping applies.
Method Cepheid GeneXpert PCR test amplifies and detects DNA of M. tuberculosis complex in clinical specimens and tests for mutations in the rpoB DNA region that can cause rifampin resistance.
Turn-around Time 48 hours from specimen receipt in this laboratory. Positive reports and suspected rifampin resistance are communicated to the specimen submitter on day of testing.
Interferences/Limitations AFB Smear and Culture performed on processed specimens concurrently at DSHS Laboratory. A negative NAA test does not mean the patient does not have M. tuberculosis complex disease. Test results must be confirmed by culture of specimen for the presence of mycobacteria.  
If a processed specimen sediment is submitted for NAA only, the AFB culture must be in progress at the submitting laboratory site. Rifampin resistance must be confirmed by sequencing (such as MDDR testing at CDC) to rule out silent or neutral mutations.
Common Causes for Rejection
  • Specimen leaked in transit. 
  • Missing identifier(s) on specimen container. 
  • No test requested on G-MYCO requisition form. 
  • Specimens received frozen, in formalin, or in culture medium will be rejected. 
Additional Information There should be a high clinical suspicion of tuberculosis when ordering this test. NAA testing should be requested if the test results will make a difference to the patient’s treatment or if the test results will make a difference to the contact investigation. Patients should not have a laboratory diagnosis of tuberculosis disease already. Exception:  If acquired rifampin resistance is suspected of a diagnosed tuberculosis patient, provider should seek a consult with TB Expert physicians who may request NAA testing to check rifampin status.