The Molecular Microbiology section deals with Polymerase Chain Reaction (PCR) based diagnostic assays for Infectious Diseases like Tuberculosis (TB), Human Immunodeficiency Virus (HIV), Hepatitis B Virus (HBV), Hepatitis C virus (HCV), etc. The laboratory is
state-of-the-art and fully equipped with advanced instrumentation like real-time PCR machines and end-point gradient PCR systems. Working protocols have been devised as per the College
of American Pathologists (CAP) guidelines; as recommended, the laboratory follows
a unidirectional work flow with designated physically separate areas for pre-amplification,
nucleic acid extraction, amplification, and post-amplification activities.
Each designated area has dedicated instruments like pipettes with aerosol barrier filter tips, centrifuges, bio-safety cabinets and deep freezers in order to minimise aerosol and PCR amplicon contamination. Testing is performed according to biosafety level II standards; the initial steps carried out for TB related tests are performed in the Mycobacteriology section up until the heat killing. Validation studies are performed for each assay prior to testing patient samples. All assays include appropriate positive and negative controls in keeping with Quality Control (QC) practices.
The laboratory participates in proficiency testing programs conducted by CAP. New reagent lots are checked against old reagent lots using clinical samples or external QC material. All instruments in the laboratory are maintained as per CAP norms with regular QC and preventive maintenance carried out at recommended intervals. Results of assay controls are reviewed for acceptability prior to reporting patient results. If QC results exceed defined acceptability limits, appropriate corrective action is initiated.
Positive TB PCR reports, reports of detection of drug resistance of Mycobacterium, are critical and informed to the consultant doctor. Reports critical for infection prevention are informed to the Infection Control Nurse. The laboratory primarily carries out molecular tests for the detection of Mycobacterium tuberculosis (MTB) in various pulmonary and extra-pulmonary specimens like sputum, bronchoalveolar lavage, pleural fluid, ascitic fluid, pus, etc., the results of which are ready in 48 hours. Further advanced testing for drug resistance in MTB is done by the Hain’s test, which can be performed from the Mycobacterium culture or an AFB smear positive clinical specimen, the results of which are ready in 48 hours.
As the laboratory is one of the few specialised in molecular biology in a large tertiary care hospital in Mumbai’s western suburbs, the patient base is growing steadily and new assays will be included in the testing menu in the future. The Molecular Microbiology section is committed to strongly support clinical decision making at the hospital with regards to molecular diagnosis of Infectious Diseases.