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HelpTest Code TB1LN Antimicrobial Susceptibility, Mycobacterium tuberculosis Complex, First Line, 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 TB2LN as an alternative. See test notification here.
Ordering Guidance
If testing for the first-line agent pyrazinamide is desired, order TBPZA / Susceptibility, Mycobacterium tuberculosis Complex, Pyrazinamide, Varies.
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 in Special Instructions.
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.
Additional Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| STV1 | Susceptibility, Mtb Complex, Broth | No, (Bill Only) | Yes |
Reflex Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| TB2LN | Susceptibility, Mtb Complex, 2 Line | Yes | No |
Testing Algorithm
When this test is ordered, the additional test will always be performed and charged separately.
If resistance to a first line antimicrobial agent is detected, reflex testing of second line agents will be performed and charged.
Special Instructions
Method Name
Broth Dilution at Critical Drug Concentrations
Reporting Name
Susceptibility, Mtb Complex, 1 LineSpecimen 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. Susceptibility testing of M tuberculosis complex isolates against these antimycobacterial agents is a key component of patient management.
The Clinical Laboratory Standards Institute (CLSI) 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 an US Food and Drug Administration cleared commercial system for rapid broth susceptibility testing of M tuberculosis complex and assesses resistance to antimycobacterial drugs at the CLSI-recommended critical concentrations.
Reference Values
Results are reported as susceptible or resistant.
Interpretation
Mycobacterium tuberculosis complex isolates are reported as susceptible or resistant to the aforementioned drugs at the critical concentrations.
Some experts believe that patients infected with strains exhibiting resistance to low levels of isoniazid but not exhibiting resistance to high levels may benefit from continuing therapy with this agent. A specialist in the treatment of tuberculosis should be consulted concerning the appropriate therapeutic regimen and dosages.
Cautions
Isolates not received in pure culture may have delayed results because isolation is required prior to testing.
Method Description
This test method is based on growth or absence of growth of Mycobacterium tuberculosis complex isolates in broth cultures containing critical concentrations of the antimycobacterial agents isoniazid, rifampin, and ethambutol. One of two FDA-cleared platforms, the BACTEC MGIT 960 (Becton Dickinson) or the VersaTREK (ThermoFisher) 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 critical concentrations of an antimycobacterial agent. Antimycobacterial agents tested are isoniazid, rifampin, and ethambutol. (Package insert: BACTEC MGIT 960 SIRE Kit, BD Diagnostics, 2016)
The VersaTrek platform measures pressure changes inside bottles containing M tuberculosis complex isolates in the presence of critical concentrations of an antimycobacterial agent. Antimycobacterial agents tested are isoniazid, rifampin, and ethambutol. (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 x 3-Antimicrobial Susceptibility, Mycobacterium tuberculosis Complex, Broth Method
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| TB1LN | Susceptibility, Mtb Complex, 1 Line | 29579-0 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| TB1LN | Susceptibility, Mtb Complex, 1 Line | 29579-0 |