Mycobacterium tuberculosis Complex Detection and Rifampin Resistance (PCR), Acid-fast Bacillus (AFB) Smear, and AFB Culture with Reflex to Identification and Susceptibility Testing (Nonsputum)

TEST: 183531
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CPT: 87116; 87206; 87556; 87798
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Special Instructions

Specimen processing (i.e., N-acetyl-L-cystine-sodium hydroxide treatment or equivalent, concentration, grinding, both or neither), mycobacterial culture and smear when appropriate (smears are not performed on blood or when there is less than 2 mL of fluid). Identification by real-time polymerase chain reaction (PCR), and/or matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry, and/or nucleic acid sequencing, will be performed at an additional charge. This culture will often detect Nocardia species and other aerobic actinomyces, and identification appropriate for these organisms will be included.

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.

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Specimen Requirements

Specimen

Bronchial washings or bronchoalveolar lavage (BAL) specimens, pleural fluid or cerebrospinal fluid (CSF)

Volume

5 mL

Minimum Volume

5 mL (Note: This volume does not allow for repeat testing.)

Container

Sterile container with screw-cap seal

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.

Stability Requirements

TemperaturePeriod
Refrigerated

Culture: 3 days

NAA: 7 days

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

This assay should not be used to test specimens from patients that have been treated with antituberculous drugs for more than three days. This 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 M. tuberculosis infection in the lungs of this patient group and difficulties encountered in obtaining adequate specimens.

This test was developed and its performance characteristics determined by Labcorp. It has not been cleared or approved by the Food and Drug Administration.

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.

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