Mycobacterium tuberculosis Complex Detection and Rifampin Resistance, NAA Without CAP-mandated Culture

CPT: 87556; 87798
Updated on 1/25/2018
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Test Details

Use

Detect and identify Mycobacterium tuberculosis complex and an rpoB mutation that is associated with rifampin resistance. Per the College of American Pathologists (CAP) guidelines (MIC.64820), a culture must be performed on all samples regardless of the molecular test result. By ordering this test, the client has assumed responsibility for performance of the AFB culture.

Limitations

The assay should not be used to test specimens from pediatric patients or from patients who have been treated with antituberculous drugs for more than three days. The assay should not be used to monitor therapy or as a test of cure. A negative test does not exclude the possibility of isolating M tuberculosis complex isolates from culture. Assay interference may occur in the presence of lidocaine, mucin, ethambutol, guaifenesin, phenylephrine, and tea tree oil.

Methodology

Nucleic acid amplification (NAA) technology; nested real-time polymerase chain reaction (PCR)

Specimen Requirements

Specimen

Sputum (adult population) first morning specimen

Volume

2 mL of raw or expectorated sputum

Minimum Volume

2 mL

Container

Sterile screw-capped vial or sterile cup; seal securely.

Patient Preparation

When collecting sputum, have the patient brush teeth or remove dentures and rinse mouth with water. Instruct the patient not to collect saliva.

Storage Instructions

Refrigerate. Specimen may be stored at a maximum of 35°C for three days and then at 2°C to 8°C for seven days. Specimen may also be stored frozen (below -70°C).

Causes for Rejection

Quantity not sufficient; inappropriate specimen source; specimen from a pediatric patient; specimen received after leaking out of transport container into the specimen bag; inappropriate or expired specimen transport device; unlabeled specimen container or container with a single patient identifier; name discrepancy between the specimen container label and the computer or the requisition; specimen received after prolonged delay (more than seven days unless frozen); specimen in a paraffin block; specimen in a fixative.

Clinical Information

References

Centers for Disease Control (CDC) and Prevention. Trends in TB Fact Sheet and Statistics. www.cdc.gov/tb/statistics/default.htm.
Fact Sheet: Cepheid Xpert® MTB/RIF Assay. Silver Spring, Md: Association of Public Health Laboratories; November 2013.
Prevention and control of tuberculosis among homeless persons. Recommendations of the Advisory Council for the Elimination of Tuberculosis. MMWR Recomm Rep. 1992 Apr 17; 41(RR-5):13-23. 1314323
Prevention and control of tuberculosis in US communities with at-risk minority populations. Recommendations of the Advisory Council for the Elimination of Tuberculosis. MMWR Recomm Rep. 1992 Apr 17; 41(RR-5):1-11. 1314322

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
183456 MTB-RIF NAA without AFB Cult. 183454 M tuberculosis complex 14556-5
183456 MTB-RIF NAA without AFB Cult. 183455 Rifampin 33634-7
183456 MTB-RIF NAA without AFB Cult. 008619 AFB Specimen Processing 8100-0

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