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Test 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.


Forms

If not ordering electronically, complete, print, and send a Microbiology Test Request (T244) with the specimen.

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.

Method Name

Broth Dilution at Critical Drug Concentrations

Reporting Name

Susceptibility, Mtb Complex, PZA

Specimen Type

Varies

Specimen 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 days

Specimen Retention Time

1 year

Performing 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