Report of Expert Consultations on Rapid Molecular Testing to Detect Drug-Resistant Tuberculosis in the United States

General Recommendations of the Expert Panel

  1. All U.S. clinicians and public health TB programs should have access to molecular DR tests to aid in the diagnosis, treatment, and control of TB.
  2. Molecular DR testing should be performed on one AFB smear-positive or NAA-positive respiratory specimen or one M. tuberculosis culture from each TB patient or TB suspect.
    1. Testing should also include specimens regardless of AFB smear result or isolates from persons that the TB Control Program designates as high priority for molecular DR testing. However, programs must be aware that the performance of molecular DR tests with AFB-smear negative specimens has not been established.
    2. Testing of a second sample (specimen or isolate) from a patient would be appropriate in situations deemed high priority by the TB program (e.g., a patient who is failing first-line therapy even though the initial molecular DR test indicated rifampin susceptibility or relapse in a patient who was non-adherent to the initial treatment plan).
  3. A phased approach to developing and implementing a molecular DR testing service is recommended. For example, the initial service could provide molecular DR testing for TB patients or suspects deemed high priority by the TB program, while CDC and partners design and implement a feasible, practical, universal molecular DR testing service.
  4. State and local TB control programs should develop, disseminate, and implement a protocol that enables health care providers in their jurisdiction to access the regional molecular DR testing services, including specifying criteria for selecting TB suspects or patients for testing. A standard test request (sample submission) form should be developed.
  5. The initial molecular DR testing service should include detection of mutations associated with rifampin resistance and those associated with isoniazid resistance. The molecular DR testing service should incorporate molecular DR tests for fluoroquinolones, aminoglycosides, and drugs for which conventional testing is problematic (e.g., ethambutol, pyrazinamide) as they are validated.
  6. Because data are not available at this time that clearly demonstrate the superiority of any of the currently validated methods over another, the panel does not recommend which test should be used in the molecular DR testing service. The decision of which test to implement in the molecular DR testing service may ultimately rest upon cost, performance, throughput, and turnaround time. Whichever technology is used, validation of the test and meeting all pertinent CLIA and FDA regulations by the molecular DR testing laboratory are essential.
  7. The molecular DR testing service should be designed such that it is able to take advantage of improvements in technologies and the understanding of the molecular basis of drug resistance.
  8. The possibility of linking NAA testing for detection of M. tuberculosis with molecular DR testing either sequentially (local laboratory to molecular DR testing laboratory) or as a combined test at the molecular DR testing laboratory should be explored to determine if it would be is a cost-effective, reliable approach to providing services to state and local TB programs.
  9. Up to four laboratories will be needed initially to provide universal molecular DR testing and their services should be coordinated with the services of the TB RTMCCs. This would provide (a) increased molecular DR testing capacity, (b) a reasonable workload per laboratory which may facilitate meeting turnaround times, (c) redundancy and surge capacity, (d) geographic distribution, (e) close collaboration with experts in the treatment of MDR TB, and (f) opportunities for rechecking and external quality control.
  10. Molecular DR testing laboratories should have the ability to test isolates and processed and non-processed specimens. Only respiratory specimens should be routinely tested. Other specimens such as CSF or tissue samples may be tested in priority situations.
    1. In a rollout phase, the molecular DR testing laboratories might primarily test processed specimens. In this phase, specimens would be collected, sent to the state or local public health laboratory, processed at the state or local laboratory, determined to be AFB-positive, and submitted to the molecular DR testing laboratory.
    2. The numbers of non-processed and processed specimens tested will depend on the protocols developed by local programs to select patients and submit specimens. TB programs must provide reliable estimates of the numbers of non-processed and processed specimens to be submitted to enable the molecular DR testing laboratories to project the costs of molecular DR testing,
  11. The interval from specimen collection to reporting of the test result to the treating clinician must be as brief as possible. Laboratories and programs should track this performance measure.
    1. Specimens must be delivered promptly to the molecular DR testing laboratory.
      1. An overnight delivery service should be used. State programs may need to provide training for local laboratorians in packaging and shipping, because delivery services such as FedEx only accept shipments packaged by a certified shipper.
      2. Laboratories must promptly package and ship samples to the molecular DR testing laboratory and avoid delays associated with batching specimens for shipment. For non-processed specimens, this is probably the day the specimen is collected. For processed specimens, this is probably the day after the specimen is received in the primary laboratory.
    2. Specimens must be tested promptly in the molecular DR testing laboratory, preferably on the day received (i.e., without introducing significant delays by batching specimens).
    3. Six day a week service is preferred.
    4. The molecular DR test results should be available within 2 business days of specimen receipt.
    5. An initial positive molecular DR test result must be treated as a critical test value. It must be immediately reported to the clinician and to public health authorities. Laboratorians should be available for consultation as to test interpretation and need for follow-up testing.
  12. Detection of rifampin resistance must trigger expedited, reflex testing for susceptibility to first-line and second-line drugs (SLD) by conventional culture-based methods and available molecular methods. This could be done at the molecular DR testing laboratory, the submitting laboratory, a state public health laboratory, a center of excellence for SLD testing, or CDC.
  13. Each TB program should designate who would be notified of the molecular DR test results.
    1. The preferred method of reporting is via electronic means such as secure email or posting results on a secure web site.
    2. The detection of drug resistance in specimen or isolate should be reported by telephone to facilitate prompt action by the program and clinician.
    3. Standardized reporting language should be developed and used.
    4. In all cases, reporting must meet requirements for maintaining patient confidentiality.
  14. Procedures for detecting and reporting discrepancies between the results of molecular and conventional testing must be developed and implemented. Clinicians should use clinical judgment and the conventional DS result for isoniazid and rifampin for case management decisions, until the discrepancy is resolved.
    1. The responsibility for identifying discrepancies lies with those having timely access to the molecular DR and conventional DS results. This may be the treating clinician, TB program or public health laboratory.
    2. Procedures must be in place for reporting discrepant results and providing consultation.
    3. Regardless of who detects a discrepancy, protocols are needed for distributing information to all involved parties and follow-up testing to resolve the discrepancy.
  15. Protocols for analyzing discrepancies between conventional and molecular DR results must be developed and implemented.
    1. The molecular DR test should be repeated on the remnant of the original specimen or a sample of the culture from the patient.
    2. The initial molecular DR result should be evaluated for concerns such as unusual amplification or evidence of a mixed population of bacteria (a low percentage of resistant bacteria may lead to false-susceptible molecular DR results).
    3. The conventional DS result should be evaluated for concerns such as contamination that might produce false-resistant results.
    4. Repeating the conventional DS tests should be considered.
    5. A sample of the culture patient should be submitted to a referee laboratory (e.g., CDC) for additional molecular (e.g., sequencing) and conventional testing.
  16. State and local TB programs should share some of the cost of the molecular DR testing. One possibility would be for programs or test requestors to pay the cost of shipping specimens to the molecular DR testing laboratories.
  17. The activities of the molecular DR testing and TB genotyping laboratories should be coordinated (possibly integrated) to avoid unnecessary duplication of efforts at the local or regional laboratory for shipping and testing of isolates.
  18. A reliable laboratory service includes procedures for internal and external quality control and a robust monitoring and evaluation plan.