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HelpTest ID TBPZA Susceptibility, Mycobacterium tuberculosis Complex, Pyrazinamide, Varies
Infectious
Ordering Guidance
To test for first-line agents, isoniazid, rifampin and ethambutol, order TB1LN / Antimicrobial Susceptibility, Mycobacterium tuberculosis Complex, First Line, Varies
Additional Testing Requirements
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 unless identification of organism is provided.
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
Confirming M tuberculosis complex resistance 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
When this test is ordered the additional test will always be performed at an additional charge.
If resistance to pyrazinamide is detected, the reflex test for confirmation of resistance 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 |
|---|---|---|
| Varies | Ambient (preferred) | |
| Refrigerated | ||
Clinical Information
Primary treatment regimens for Mycobacterium tuberculosis complex often include isoniazid, rifampin, ethambutol, and pyrazinamide (PZA). Susceptibility testing of each M tuberculosis complex isolate against these first-line antimycobacterial agents is a key component of patient management.
The Clinical and Laboratory Standards Institute (CLSI) provides consensus protocols for the methods, antimycobacterial agents, and critical concentrations of each agent to be tested in order to permit standardized interpretation of M tuberculosis complex susceptibility test results. Current recommendations indicate that laboratories should use a rapid broth method in order to obtain M tuberculosis complex susceptibility data as quickly as possible to help guide patient management. According to the CLSI, resistance can be confirmed by another method or by another laboratory at the discretion of the testing laboratory.
This test uses an FDA-cleared commercial system for rapid broth susceptibility testing of M tuberculosis complex against PZA. Since the literature indicates that broth testing of PZA can, at times, produce falsely resistant results, resistance to PZA by the broth method is automatically confirmed by pncA DNA sequencing. The pncA gene of M tuberculosis complex is responsible for activation of the prodrug PZA and hence PZA activity. Variations 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 first-line 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.
Cautions
For resistant organisms, confirmatory testing using pncA DNA sequencing is automatically performed and the presence or absence of pncA variations associated with pyrazinamide resistance is reported.
In vitro susceptibility does not guarantee clinical response. Therefore, the decision to treat with a particular agent should not be based solely on the antimicrobial susceptibility testing result.
Susceptibility testing should be performed on pure culture isolates of Mycobacterium tuberculosis complex.
Some variants associated with pyrazinamide resistance that may occur outside of the pncA promoter and gene region and may therefore not be confirmed by DNA sequencing of this target.
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)