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HelpTest Code TBPZA Susceptibility, Mycobacterium tuberculosis Complex, Pyrazinamide, Varies
Infectious
Test Down Notes
Effective August 08, 2024:  This test is temporarily unavailable due to reagent supply. The downtime is expected to be >30 days. Order MTBPZ as an alternative. See test notification here.
Ordering Guidance
To test for first-line agents, isoniazid, rifampin and ethambutol, order TB1LN / Antimicrobial Susceptibility, Mycobacterium tuberculosis Complex, First Line, Varies.
Isolates identified as Mycobacterium bovis and Myocobacterium bovis bacille Calmette-Guerin (BCG) will not be accepted as they are intrinsically resistant to pyrazinamide.
Additional Testing Requirements
If organism identification is not provided, CTB / Mycobacteria and Nocardia Culture, Varies or CTBID / Culture Referred for Identification, Mycobacterium and Nocardia, Varies must also be ordered and will be charged separately.
Shipping Instructions
1. See Infectious Specimen Shipping Guidelines
2. Place specimen in a large infectious container (T146) and label as an etiologic agent/infectious substance.
Necessary Information
Specimen source and suspected organism identification are required.
Specimen Required
Specimen Type: Organism
Supplies: Infectious Container, Large (T146)
Container/Tube: Middlebrook 7H10 agar slant
Specimen Volume: Isolate
Collection Instructions: Organism must be in pure culture, actively growing.
Useful For
Susceptibility testing of Mycobacterium tuberculosis complex isolates growing in pure culture against pyrazinamide
This test is not useful for Mycobacterium bovis and Myocobacterium bovis bacille Calmette-Guerin (BCG) isolates as they are intrinsically resistant to pyrazinamide.
Additional Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| STVP | Susceptibility, Mtb Complex, PZA | No, (Bill Only) | Yes |
Reflex Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| MTBVP | Mtb PZA Confirmation, pnc A Sequence | No, (Bill Only) | No |
Testing Algorithm
If resistance to pyrazinamide is detected, the reflex sequencing test or confirmation of resistance will be performed at an additional charge.
If the broth microdilution test is unable to be performed (eg, due to reagent shortages, failure of the isolate to grow in the test medium), the reflex sequencing test will be performed at an additional charge.
Special Instructions
Method Name
Broth Dilution at Critical Drug Concentrations
Reporting Name
Susceptibility, Mtb Complex, PZASpecimen Type
VariesSpecimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Varies | Ambient (preferred) | ||
| Refrigerated | |||
Reject Due To
| Agar plate | Reject |
Clinical Information
Initial treatment regimens for Mycobacterium tuberculosis complex often include isoniazid, rifampin, ethambutol, and pyrazinamide (PZA). Susceptibility testing of M tuberculosis complex isolates against these antimycobacterial agents is a key component of patient management.
The Clinical and Laboratory Standards Institute provides consensus protocols for the methods, antimycobacterial agents, and critical concentrations of each agent to be tested to permit standardized interpretation of M tuberculosis complex susceptibility test results.
This test uses a US Food and Drug Administration cleared commercial system for rapid broth susceptibility testing of M tuberculosis complex against PZA. The literature indicates that broth testing of PZA can, at times, produce falsely resistant results, so resistance to PZA by the broth method is automatically confirmed by pncA DNA sequencing. Variants in the pncA gene and upstream promoter region have been reported to account for the majority (70%-97%) of PZA-resistant isolates. However, 3% to 30% of PZA-resistant isolates do not have a corresponding pncA variant and other genes (eg, rpsA) may also play a role.
A separate test is available for testing of the other primary agents (isoniazid, rifampin and ethambutol). If desired, this must be ordered separately; TB1LN / Antimicrobial Susceptibility, Mycobacterium tuberculosis Complex, First Line, Varies.
Reference Values
Results are reported as susceptible or resistant.
Interpretation
Mycobacterium tuberculosis complex isolates are reported as susceptible or resistant to pyrazinamide at the critical concentration.
Cautions
For isolates determined to be resistant by the broth method, confirmatory testing using pncA DNA sequencing is automatically performed and the presence or absence of pncA variations associated with pyrazinamide resistance is reported. Some variants associated with pyrazinamide resistance may occur outside of the pncA promoter and gene region and may therefore not be confirmed by DNA sequencing of this target. Presence of a pncA mutation associated with resistance confirms the broth susceptibility testing results. Absence of a pncA mutation does not rule out possible resistance.
Susceptibility testing should be performed on pure culture isolates of Mycobacterium tuberculosis complex.
Method Description
This test is based on presence or absence of growth of an Mycobacterium tuberculosis complex isolate in broth cultures in the presence of critical concentrations of the antimycobacterial drug pyrazinamide. One of two FDA-cleared platforms (BD MGIT 960 or the VersaTREK) will be used. (Brown-Elliott, BA, Cirillo DM, Musser KA, Rowlinson M-C. Susceptibility Test Methods: Mycobacteria, Nocardia, and Other Actinomycetes. In: Carroll KC, Pfaller MA, eds. Manual of Clinical Microbiology, 13th Edition. ASM Press, 2023)
The BACTEC MGIT 960 platform measures fluorescence in a Mycobacterial Growth Indicator Tube (MGIT) containing an M tuberculosis complex isolate in the presence of a critical concentrations of pyrazinamide (Package insert: BACTEC MGIT 960 SIRE Kit, BD Diagnostics, 9/2019)
The VersaTrek platform inside bottles containing M tuberculosis complex isolates in the presence of a critical concentration of the antimycobacterial PZA. (Package insert: VersaTREK Mycobacteria Detection and Susceptibility Testing system, TREK Diagnostics, 04/2014)
Day(s) Performed
Monday through Sunday
Report Available
10 to 21 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.CPT Code Information
87188-Susceptibility, Mycobacterium tuberculosis Complex, Pyrazinamide
87153-Mtb PZA Confirmation, pncA Sequencing (if appropriate)
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| TBPZA | Susceptibility, Mtb Complex, PZA | 56026-8 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| TBPZA | Susceptibility, Mtb Complex, PZA | 56026-8 |