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HelpTest Code LABTB2LN Susceptibility, Mycobacterium tuberculosis Complex, Second Line, Varies
Infectious
Additional Codes
| Test Name in EPIC | EPIC Test Code | Mnemonic | Mayo Test ID |
|---|---|---|---|
| Susceptibility, Mtb Complex, 2 Line | LABTB2LN | TB2LN | TB2LN |
Useful For
Determination of Mycobacterium tuberculosis complex minimal inhibitory concentrations to second-line antimicrobial agents
Additional Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| STV2 | Susceptibility, Mtb Cx, 2nd Line | No, (Bill Only) | Yes |
Testing Algorithm
When this test is ordered, the additional test will always be performed at an additional charge.
Special Instructions
Reporting Name
Susceptibility, Mtb Complex, 2 LineSpecimen Type
VariesAdditional 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. For shipping information see Infectious Specimen Shipping Guidelines.
2. Place specimen in a large infectious container 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.
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Varies | Ambient (preferred) | ||
| Refrigerated | |||
Reject Due To
| Other | Agar plate |
Clinical Information
The Clinical and Laboratory Standards Institute (CLSI) provides a consensus protocol for the methods, antimycobacterial agents, and critical concentrations of each agent to be tested in order to permit standardized interpretation of Mycobacterium tuberculosis complex susceptibility testing results. CLSI guidelines suggest that second-line agents should be tested when an isolate of M tuberculosis complex is resistant to rifampin, is monoresistant to the critical concentration of isoniazid and the physician intends to use a fluoroquinolone for therapy, or is resistant to any combination of 2 first-line agents.
This test uses a broth microdilution method for susceptibility testing of M tuberculosis complex against second-line agents. Agents tested are amikacin, ethionamide, kanamycin, moxifloxacin, ofloxacin, p-aminosalicylic acid, rifabutin, and streptomycin. In contrast to other M tuberculosis complex susceptibility methods which test 1 or 2 critical concentrations of a drug, this method examines a range of drug concentrations and produces a minimal inhibitory concentration result.
Reference Values
Interpretive criteria and reporting guidelines are followed using the Clinical Laboratory Standards Institute (CLSI) M24S document.
Interpretation
Results are reported as minimal inhibitory concentrations in mcg/mL.
This test is used as an alternative to TB1LN / Antimicrobial Susceptibility, Mycobacterium tuberculosis Complex, First Line, Varies when reagents are not available to perform the TB1LN test. Ethambutol, isoniazid, and rifampin agents are not routinely reported with this test.
Cautions
Consensus guidelines for interpretive criteria using this method are not available at this time. Breakpoints were established by Mayo Clinic by comparison to the critical concentration for each drug and are considered tentative until consensus guidelines are established.
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.
Drug susceptibility testing should be performed on pure culture isolates of Mycobacterium tuberculosis complex.
Method Description
This test utilizes the MycoTB broth microtiter dilution plate (Trek Diagnostic Systems, Inc.). Antimicrobials included in the assay are tested according to the Clinical and Laboratory Standards Institute guidelines. The plate contains lyophilized antimicrobials which are rehydrated prior to testing. A standardized suspension of the Mycobacterium tuberculosis isolate is added to the plate wells and the plate is incubated at 36° C in 5% to 10% carbon dioxide for up to 14 days. The first drug-containing well with no visible growth is determined to be the endpoint.(Clinical and Laboratory Standards Institute (CLSI). Susceptibility Testing of Mycobacteria, Nocardia spp., and Other Aerobic Actinomycetes. CLSI standard M24. Clinical and Laboratory Standards Institute (CLSI). Performance Standards for Susceptibility Testing of Mycobacteria, Nocardia spp., and Other Aerobic Actinomycetes. CLSI supplement M24S; Hall L, Jude KP, Clark SL, et al. Evaluation of the Sensititre MycoTB plate for susceptibility testing of the Mycobacterium tuberculosis complex against first- and second-line agents. J Clin Microbiol. 2012;50:3732-3734; Thermo Scientific Sensititre MIC Susceptibility Plates for Mycobacterium tuberculosis. Product Insert. 011 - MYCOTB - CID9502. Revision Date: 09/07/2016)
Day(s) Performed
Monday through Sunday
Report Available
21 to 30 daysSpecimen Retention Time
2 yearsPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
87186-Susceptibility, Mtb Cx, 2nd Line
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| TB2LN | Susceptibility, Mtb Complex, 2 Line | 29579-0 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| TB2LN | Susceptibility, Mtb Complex, 2 Line | 29579-0 |
Method Name
Minimum Inhibitory Concentration (MIC) by Microtiter Broth Dilution Method
Specimen Minimum Volume
See Specimen Required