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Mycobacterium tuberculosis Complex Detection and Rifampin Resistance, NAA with AFB Culture
CPT:
87116; 87556; 87798
Expected Turnaround Time
48 - 56 days
Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.
Related Documents
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
Storage Instructions
Refrigerate. If sample is to be split for other tests, specimen should be divided at the time of collection so that each portion is transported at the appropriate temperature.
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Refrigerate. |
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Refrigerate. If sample is to be split for other tests, specimen should be divided at the time of collection so that each portion is transported at the appropriate temperature. |
Stability Requirements
| Temperature | Period |
|---|---|
| Refrigerated | Culture: 3 days NAA: 7 days |
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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.
Causes for Rejection
Quantity not sufficient; inappropriate specimen source; 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
Test Details
Use
This test is used to detect and identify Mycobacterium tuberculosis complex and an rpoB mutation that is associated with rifampin resistance.
Limitations
The assay should not be used to test specimens from patients that 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.
Lower sensitivity may be observed in pediatric patients due to the diffuse nature of Mtb infection in the lungs of this patient group and difficulties encountered in obtaining adequate specimens.
Methodology
Nucleic acid amplification (NAA), nested real-time polymerase chain reaction (PCR); concentrated specimen with broth-based and/or agar-based culture. Culture is held for six weeks before negative is reported. Organisms from culture are identified by use of real-time polymerase chain reaction (PCR) and/or MALDI-TOF and/or nucleic acid sequencing.
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
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