Report of Expert Consultations on Rapid Molecular Testing to Detect Drug-Resistant Tuberculosis in the United States
Appendix 3
Figure 1: Flow Chart of Steps in a Molecular Drug-Resistance Testing Service
Figure 2: Reflex Testing
Steps in Molecular Drug-Resistance Testing
Before initiating a program for molecular drug susceptibility testing, each jurisdictional TB program must decide how to accomplish the steps below and develop any necessary protocols for
- determining which TB suspects and patients get molecular DR testing (i.e., establish selection criteria) and which types of specimens to test,
- authorization of molecular DR testing for TB suspects and patients
- shipment of specimens and isolates to molecular DR testing laboratory
- reporting of molecular DR test results
- reflex testing for rifampin-resistant samples
- discrepant result analysis
It is anticipated that as part of developing this service, a work group of CDC, NTCA, and APHL representatives will develop guidelines, models, and templates for these steps and protocols.
A TB suspect or patient presents for evaluation:
- Local health care provider or TB program
- evaluate TB suspect or patient, determine if molecular DR testing is warranted; consult with TB program or TB experts as necessary
- if required, obtain permission from the TB program to request a molecular DR test for a TB suspect or patient,
- obtain specimen
- complete submission form. The submission form should indicate if this is a new suspect or patient that has not previously had a sample sent for molecular DR testing.
- submit to lab for processing, AFB smear microscopy, and culture and possible submission to molecular DR testing laboratory
- if approved by the TB program, assign a unique identifier, properly package, and submit non-processed specimen to the molecular DR testing laboratory. Ensure that a specimen has been sent for microscopy and culture
- Local laboratory
- receive specimen, assign identifier, enter data into laboratory information system
- process specimen in accord with local requirements
- Specimens which are processed and cultured at a local laboratory
- digest, decontaminate, concentrate, AFB smear microscopy, inoculate media
- store remnants of the processed specimen for possible shipment to molecular DR testing laboratory
- if cultures are to be tested, confirm that the culture contains AFB
- Specimens handled at laboratories that only do AFB smear microscopy
- process, AFB smear microscopy
- refer specimen to full-service laboratory for isolation and drug susceptibility testing
- store remnants of the processed specimen for possible shipment to molecular DR testing laboratory
- Specimens which are processed and cultured at a local laboratory
- If AFB-positive or NAA positive (specimen or culture),
- Confirm or obtain approval of the TB program to submit to molecular DR testing laboratory
- Package sample and ship to molecular DR testing laboratory in accord with local policies
- If AFB-negative, ship to molecular DR testing laboratory ONLY if requested to do so by TB program
- Molecular DR testing laboratory
- accession sample, enter data into a laboratory information management system.
- process sample for molecular DR testing
- non-processed specimens: digest, recover bacteria, lyse bacteria , prepare molecular DR test substrate. Note: AFB smear microscopy should be performed to aid in the interpretation of the Molecular DR test result.
- processed specimens: recover bacteria, lyse bacteria, prepare molecular DR test substrate
- cultures: recover bacteria, lyse bacteria, prepare molecular DR test substrate
- conduct molecular DR testing
[one or two step test: detect M. tuberculosis then molecular DR test or combined detection and molecular DR testing]- include appropriate positive and negative controls
- if inhibitors detected or suspected, conduct appropriate follow-up testing
- if results are indeterminate, conduct appropriate follow-up testing
- review result, prepare report using standardized language, and sign out
- report result in accord with TB program instructions
- recipients of report to be determined by TB program
- report rifampin-susceptible results electronically
- report rifampin-resistant results by phone and electronically
- store residual sample for potential follow-up testing
- Recipient of report
- if necessary, ensure all involved parties are promptly informed of result and act upon the result
- if rifampin resistance detected, initiate reflex testing
- testing to include expedited conventional DS testing for 1st and 2nd line drugs
- testing to be done at a proficient laboratory identified by program
- compare molecular and conventional DS results, report and discrepancies to TB Control program
- Health care provider/clinician
- receive report, incorporate results into case management decisions
- obtain result of conventional drug susceptibility testing
- compare molecular and conventional DS results, report and discrepancies to TB Control program
-- conventional tests considered the gold standard for isoniazid and rifampin
- Page last reviewed: September 1, 2012
- Page last updated: September 1, 2012
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