Tuberculosis PCR and Culture, Respiratory
Test Mnemonic
TBPCRX
Primary CPT Codes
- 87015 - QTY (1), Processing, AFB Concentration
- 87116 - QTY (1), Culture, Acid Fast
- 87206 - QTY (1), Smear, Acid Fast Fluorescent
- 87564 - QTY (1), Amplification, Mycobacterium tuberculosis
Variable CPT Codes (dependent on findings)
- 87118 - QTY (1), Identification, Mycobacterial
- 87186 - QTY (1), Susceptibility, Multi-antimicrobial AFB
Aliases
- mycobacteria
- Mycobacterium
- TB
Performing Laboratory
Cleveland Clinic Laboratories
Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 5 mL | Sputum | Clean, leakproof container | See note | Refrigerated | Sputum may be expectorated or induced. For patients suspected of having pulmonary tuberculosis, PCR testing of at least 1 high quality sputum sample and culture of 3 sputum specimens (collected at least 8 hours apart with at least one first morning specimen) are recommended. Volume: 5 mL (preferred); 1 mL minimum. |
| 10 mL | Bronchoscopy specimen | Clean, leakproof container | See note | Refrigerated | Larger volumes improve recovery. Collect BAL, wash, or aspirate into sputum trap or sterile cup. Volume: at least 10 mL (preferred). Place bronchial brush in sterile, leak-proof tube or cup with enough non-bacteriostatic sterile saline to cover the brush (1-10 ml). |
Stability
| Environmental Condition | Description |
|---|---|
| Refrigerated | Respiratory samples can be stored at 2-8°C for up to seven days. Sputum concentrates can be stored at 2-8°C for up to seven days. |
| Ambient | Respiratory specimens can be stored at a maximum of 35°C for up to three days. |
Days Performed
7 days a week
Turnaround Time
1 - 2 days
Methodology
| Name | Description |
|---|---|
| Real-Time Polymerase Chain Reaction (RT-PCR) |
Special Info
Species and subspecies within the M. tuberculosis complex are not distinguished. If positive for M. tuberculosis complex a result for rifampin resistance is reported. Although 95% of mutations conferring rifampin resistance will be detected, other resistance mutations are possible. Similarly, false positive rifampin resistance may occur due to mutations that do not confer resistance. In vitro susceptibility testing is required.
Clinical Info
The Xpert MTB/RIF assay should be performed on specimens from patients for whom there is clinical suspicion of tuberculosis and who have received less than 3 days of anti-tuberculosis therapy. PCR is recommended for rapid detection of M. tuberculosis in respiratory specimens. PCR is 98% sensitive for detection of smear positive/culture positive pulmonary infection. M. tuberculosis may also be detected in smear-negative sputum samples because of the greater sensitivity of the MTB/RIF assay compared to acid fast microscopy. A positive result may occur in the presence of non-viable M. tuberculosis. A negative result does not rule-out infection. Culture is always performed when PCR is requested because culture is more sensitive. The predictive value for the absence of smear positive/culture positive tuberculosis is 99.7% for one negative Xpert PCR assay and 100% for two negative Xpert PCR assays. Therefore, the Xpert assay can be used to help determine if continued isolation is warranted in patients with suspected pulmonary tuberculosis. (Steingart Cochran Rev 2013; Luetkemeyer CID 2016)