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HelpTest ID TB2LN Susceptibility, Mycobacterium tuberculosis Complex, Second Line
Infectious
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 and charged separately.
Special Instructions
Method Name
Minimum Inhibitory Concentration (MIC) by Microtiter Broth Dilution Method
Reporting Name
Susceptibility, Mtb Complex, 2 LineSpecimen Type
VariesSpecimen Type: Organism
Container/Tube: Middlebrook 7H10 agar slant
Specimen Volume: Isolate
Collection Instructions:
1. Organism must be in pure culture, actively growing.
2. Place specimen in a large infectious container (Supply T146) and label as an etiologic agent/infectious substance.
Additional Information:
1. Specimen source and suspected organism identification are required.
2. CTB / Mycobacterial Culture or CTBID / Culture Referred for Identification, Mycobacterium must also be ordered and will be charged separately unless identification of organism is provided.
3. See Infectious Specimen Shipping Guidelines in Special Instructions for shipping information.
Forms: If not ordering electronically, complete, print, and send a Microbiology Test Request Form (T244) with the specimen (http://www.mayomedicallaboratories.com/it-mmfiles/microbiology_test_request_form.pdf).
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Varies | Ambient (preferred) | |
| Refrigerated | ||
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 Mycobacterium 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 Mycobacterium tuberculosis complex against second-line agents. Agents tested are amikacin, cycloserine, ethionamide, kanamycin, moxifloxacin, ofloxacin, p-aminosalicylic acid, rifabutin, and streptomycin. In contrast to other Mycobacterium tuberculosis susceptibility methods which test 1 or 2 critical concentrations of a drug, this method examines a range of drug concentrations and produces an minimal inhibitory concentration result.
Reference Values
Results are reported as minimal inhibitory concentration (MIC) values with units of mcg/mL and tentative interpretations of susceptible or resistant are provided.
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.
Day(s) Performed
Monday through Sunday; Varies
Report Available
21-28 daysPerforming Laboratory
Mayo Medical Laboratories in Rochester
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.CPT Code Information
87186-Susceptibility, Mtb Cx, 2nd Line