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5 Detecting Drug Resistance and Strengthening Laboratory Capacity
5 Detecting Drug Resistance and Strengthening Laboratory Capacity
Pages 59-70
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From page 59... ...
• he Supranational Reference Laboratory Network has played a T key role in determining the extent of drug resistance by conducting representative surveys in broad regions, assessing the quality of TB programs, and informing policy decisions. • he establishment of national reference laboratories, intermedi T ate reference laboratories, and laboratories in medical colleges, together with plans for dozens more laboratories for liquid plus molecular testing, will increase laboratory capacity.
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From page 60... ...
Culture methods, which are regarded as the gold standard, are still widely used today, but have limitations, including • long turnaround time; • failure to provide precise identification of species; • possibility of negative cultures for patients on treatment; • laborious testing procedures, including standardization of critical concentrations and establishment of appropriate inoculum size; and • issues concerning the stability of the drug in different culture media, the reliability of results, and quality assurance. Several rapid assays measure resistance directly from clinical specimens.
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From page 61... ...
Universally accepted standards for critical concentrations are needed to ensure the reproducibility of DST on second-line drugs. One study, for example, found that 21 supranational reference laboratories had different critical concentrations as a result of variations in testing systems and media (Kim et al., 2004)
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From page 62... ...
, GeneXpert MTB/RIF outperformed smear tests, yielding a relative increase in case detection and accurately ruling out MDR TB. Even in countries with little MDR TB, there is value to using GeneXpert to diagnose TB as it is much more sensitive than microscopy and faster than and as sensitive as culture tests.
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From page 63... ...
; performing the gold standard test on separate groups with and without disease; performing the experimental test on all subjects and classifying them as test positives or test negatives; and developing a 2–by–2 table to calculate sensitivity, specificity, predictive values, likelihood ratios, and diagnostic odds ratios. With respect to molecular tests for drug resistance, a variety of phenotypic tests can serve as the gold standard, including liquid or solid culture and clinical outcomes.
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From page 64... ...
Methods used for external quality assurance include sending an isolate with a known mutation to a laboratory to determine whether the right answer has been obtained; comparing results of another molecular or phenotypic test with the test results; or using laboratory performance indicators, such as the level of agreement among results of molecular or phenotypic tests, the concordance between different samples from the same patient, or the percentage of indeterminate results. The accuracy of a test determines its value to the clinician.
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From page 65... ...
Today the Supranational Reference Laboratory Network determines drug resistance globally through representative surveys in broad regions. It seeks to differentiate between previously treated and untreated cases while continuing to assess the quality of TB programs.
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From page 66... ...
It monitors India's other national reference laboratories, intermediate reference laboratories, regional medical research centers, and private laboratories. The Supranational Reference Laboratory Network has made substantial contributions to policy making.
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From page 67... ...
• External quality testing for the LPA needs to be considered because intermediate resistance to rifampicin has emerged as a problem. • The role of operational research in national reference laboratories or supranational reference laboratories is not clearly defined.
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From page 68... ...
It also is supporting 40 laboratories for LPA equipment and consumables, and 31 laboratories for liquid culture equipment and consumables. The Global Fund Round 9 project further supports these laboratories in the implementation of the national laboratory scale-up plan through human resources, equipment, on-site technical support, and longterm mentoring and provides funds for human resource development and related costs for on-site technical support.
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From page 69... ...
The strengths of the Indian laboratory scale-up experience thus far have been • strong coordination at all levels in implementing the drug-resistant TB response plan; • quarterly national-level meetings by the Central TB Division, with the participation of the national reference laboratories and all implementing partners; • strong coordinated efforts in human resource development; • proactive program leadership at the central and state levels; • fast-track budget mobilization at the state level; and • contributions of WHO and RNTCP consultants in addressing field problems. Key challenges have included • dealing with delays in the development of an online management information system; • ensuring an uninterrupted supply of second-line drugs; • maintaining laboratory proficiency despite drug shortages; and • delivering treatments as volume increases and turnaround times decrease.
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From page 70... ...
• Fostering a greater number of suppliers of new TB diagnostics would affect market dynamics and achieve a further cost reduction for rapid diagnostics.
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