Skip directly to search Skip directly to A to Z list Skip directly to navigation Skip directly to site content Skip directly to page options
CDC Home

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

  1. determining which TB suspects and patients get molecular DR testing (i.e., establish selection criteria) and which types of specimens to test,
  2. authorization of molecular DR testing for TB suspects and patients
  3. shipment of specimens and isolates to molecular DR testing laboratory
  4. reporting of molecular DR test results
  5. reflex testing for rifampin-resistant samples
  6. 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:

  1. Local health care provider or TB program
    1. evaluate TB suspect or patient, determine if molecular DR testing is warranted; consult with TB program or TB experts as necessary
    2. if required, obtain permission from the TB program to request a molecular DR test for a TB suspect or patient,
    3. obtain specimen
    4. 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.
    5. submit to lab for processing, AFB smear microscopy, and culture and possible submission to molecular DR testing laboratory
    6. 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

  2. Local laboratory
    1. receive specimen, assign identifier, enter data into laboratory information system
    2. process specimen in accord with local requirements
      1. Specimens which are processed and cultured at a local laboratory
        1. digest, decontaminate, concentrate, AFB smear microscopy, inoculate media
        2. store remnants of the processed specimen for possible shipment to molecular DR testing laboratory
        3. if cultures are to be tested, confirm that the culture contains AFB
      2. Specimens handled at laboratories that only do AFB smear microscopy
        1. process, AFB smear microscopy
        2. refer specimen to full-service laboratory for isolation and drug susceptibility testing
        3. store remnants of the processed specimen for possible shipment to molecular DR testing laboratory
    3. If AFB-positive or NAA positive (specimen or culture),
      1. Confirm or obtain approval of the TB program to submit to molecular DR testing laboratory
      2. Package sample and ship to molecular DR testing laboratory in accord with local policies
    4. If AFB-negative, ship to molecular DR testing laboratory ONLY if requested to do so by TB program

  3. Molecular DR testing laboratory
    1. accession sample, enter data into a laboratory information management system.
    2. process sample for molecular DR testing
      1. 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.
      2. processed specimens: recover bacteria, lyse bacteria, prepare molecular DR test substrate
      3. cultures: recover bacteria, lyse bacteria, prepare molecular DR test substrate
    3. conduct molecular DR testing
      [one or two step test: detect M. tuberculosis then molecular DR test or combined detection and molecular DR testing]
      1. include appropriate positive and negative controls
      2. if inhibitors detected or suspected, conduct appropriate follow-up testing
      3. if results are indeterminate, conduct appropriate follow-up testing
    4. review result, prepare report using standardized language, and sign out
    5. report result in accord with TB program instructions
      1. recipients of report to be determined by TB program
      2. report rifampin-susceptible results electronically
      3. report rifampin-resistant results by phone and electronically
    6. store residual sample for potential follow-up testing
  4. Recipient of report
    1. if necessary, ensure all involved parties are promptly informed of result and act upon the result
    2. if rifampin resistance detected, initiate reflex testing
      1. testing to include expedited conventional DS testing for 1st and 2nd line drugs
      2. testing to be done at a proficient laboratory identified by program
    3. compare molecular and conventional DS results, report and discrepancies to TB Control program

  5. Health care provider/clinician
    1. receive report, incorporate results into case management decisions
    2. obtain result of conventional drug susceptibility testing
    3. compare molecular and conventional DS results, report and discrepancies to TB Control program
      -- conventional tests considered the gold standard for isoniazid and rifampin

Contact Us:
  • Centers for Disease Control and Prevention
    Division of Tuberculosis Elimination (DTBE)
    1600 Clifton Rd., NE
    MS E10
    Atlanta, GA 30329
  • 800-CDC-INFO
    TTY: (888) 232-6348
  • Contact CDC–INFO
  • Page last reviewed: September 1, 2012
  • Page last updated: September 1, 2012 The U.S. Government's Official Web PortalDepartment of Health and Human Services
Centers for Disease Control and Prevention   1600 Clifton Rd. Atlanta, GA 30329-4027, USA
800-CDC-INFO (800-232-4636) TTY: (888) 232-6348 - Contact CDC-INFO