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Precautions to Ensure Reliability of a Test for Diagnosis of DR-TB
Learning Objectives-
Describe the methods used under the NTEP to ensure the reliability of Drug-resistant Tuberculosis (DR-TB) diagnostic tests:
a) Quality Assurance (QA) and control of tests
b) Proficiency testing
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The National Tuberculosis Elimination Program (NTEP) uses the following methods to ensure the reliability of Drug-resistant Tuberculosis (DR-TB) diagnostic tests:
- Quality Assurance (QA) and control of tests
- Proficiency testing
Quality Assurance and Control of Tests
NTEP has a well-established quality assurance mechanism which follows the WHO system of hierarchical control from the highest level of National Reference laboratories to State Intermediate Reference laboratories, to the district/sub district level and then, TB diagnostic centres at the most peripheral level.
The QA has all elements of Internal Quality Control (IQC), On-site Evaluation (OSE) and External Quality Control (EQC).
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QA ACTIVITIES FOR DR-TB DIAGNOSTIC TESTS |
COMPONENTS OF QA |
|---|---|
|
External QA (EQA) for sputum smear microscopy |
On-site evaluation, panel testing and Random Blinded Rechecking (RBRC) |
|
Culture and Drug Susceptibility Testing (C&DST) |
IQC and EQA mechanisms |
|
IQC of Lowenstein Jensen (LJ) media |
Testing each batch of media for contamination as well as the use of control strain (H37RV) for growth parameters |
|
IQC for Mycobacteria Growth Indicator Tube (MGIT) |
Instrument guided |
|
IQC of DST |
Involves use of control strain (H37RV) as well as mono-resistant strains with every batch of DST performed |
|
EQA for DST |
Done through structured panel testing and retesting exercises |
Proficiency Testing
- Proficiency testing (PT) is the measure used to examine the proficiency of the technician/professional performing the test to conduct it. Annual PTs ensure that the technicians/professionals are performing the tests as intended and their proficiency is satisfactory.
- PT exercise is conducted annually to certify laboratories in all technologies used for determination of drug resistance.
- PT for line-probe assay (LPA) includes benchmarks for invalid results, contamination in negative control, internal and external concordance.
- PT is also conducted for phenotypic DST, Cartridge-based Nucleic Acid Amplification Tests (CBNAAT) (internal and external controls) and TrueNat tests.
- Coordination of external quality assurance activity, manufacture and validation of the panels is undertaken by National TB Institute, Bangalore.
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