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Standards for Laboratory Diagnosis of Tuberculosis

Standards for Laboratory Diagnosis of Tuberculosis. Professor Brian I. Duerden Inspector of Microbiology and Infection Control, Department of Health. TB diagnosis and management depend upon a reliable and prompt laboratory service. Guidance and Standards. National SOP How to do the tests

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Standards for Laboratory Diagnosis of Tuberculosis

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  1. Standards for Laboratory Diagnosis of Tuberculosis Professor Brian I. Duerden Inspector of Microbiology and Infection Control, Department of Health

  2. TB diagnosis and management depend upon a reliable and prompt laboratory service

  3. Guidance and Standards • National SOP • How to do the tests • NICE guidance • How to manage the patient • DH programme • What service should be delivered • 3 working groups

  4. TB monitoring and laboratory services working group • Surveillance standards • Standards for laboratory diagnosis • Current best practice • Simple and straightforward • Not replicate or replace the National SOP

  5. Samples Transfer to laboratory Immediate tests Microscopy Culture, isolation and identification Laboratory facilities and expertise Transport Susceptibility testing Molecular fingerprinting/typing Notification PCR detection of Mtb Immunodiagnostic tests Histopathology Standards to cover

  6. Samples • Type of sample • Sputum (resp. sample), CSF (spinal/para-spinal/intra-cerebral), gastric washings, lymph nodes (tissues), urine, faeces • Number of samples • 2 or 3 for sputum? Consecutive days. • Early morning or any time? • True LRT specimen • Documentation

  7. Transfer to laboratory • Within 24h (or 1 working day, max 48h) • Minimise overgrowth • Maintain AFB character • Potentially infected clinical sample • Routine procedure

  8. Immediate tests • Microscopy • Auramine fluorescent staining • 6-day service (not on call) • Perform microscopy and issue result within 24h (1 working day) of receipt • Telephone positive result to senior member of clinical team • Notify lead TB nurse, lead clinician, CCDC • Accreditation; IQC programme; satisfactory EQA performance; staff CPD/peer review

  9. Culture, isolation and identification • Automated liquid culture on all samples • Set up within 24h of receipt (6 day service) • Plus conventional solid culture • Send all isolates to RCM on day found to be positive • Reach RCM within 24h • Complete identification of most mycobacterial isolates within 21 days

  10. Identification and reporting • NAAT (PCR, LCR) or hybridisation gene probe for Mtb complex • On the day culture shows positive OR • Within 24h of receipt at RCM • Other probes and/or phenotypic tests • Report on day of test to • Senior member of clinical team • Lead TB nurse, lead TB clinician, CCDC

  11. Laboratory facilities and expertise • Safety – Category 3 for culture • HSE approved • Contingency plan for accidental dispersal • Continuity plan for closure • Accredited • IQC programme, satisfactory EQA • Sufficient number – daily service, competence • Named Consultant and BMS for advice

  12. Transport • Samples • Potentially infected samples (routine) • Positive cultures • Category A but exemption to treat as B for clinical and diagnostic purposes • UN 3373 – marked Diagnostic or Clinical • P650 packaging • Do not send by Royal Mail

  13. Susceptibility testing • Complete within 30 days of initial receipt of clinical sample for primary agents • Isoniazid, rifampicin, pyrazinamide, ethambutol • Takes 10-20 days by liquid proportion (automated) or resistance ratio • Molecular detection • Rifampicin within 24h if MDRTB suspected • Isoniazid under development • Done at RCM with accreditation, IQC, EQA

  14. Molecular fingerprinting/typing • ALL ISOLATES • 15-loci MIRU-VNTR • Mycobacterial Interspersed Repetitive Units – Variable Number Tandem Repeats • Results to national database • Other techniques as appropriate • Done at RCM

  15. Laboratory notification • HPA • Via CoSurv from laboratory that identifies a positive culture • Confirmation of positive from RCM within 24h (1 working day) of receipt • RCM reports culture and susceptibility results to MycobNET within 24h of report to clinician

  16. PCR detection of Mtb • Not routine • Available from RCM for particular samples • High suspicion • Definitive diagnosis deemed to be urgent • Liaise in advance – Consultany Microbiologist to RCM

  17. Immunodiagnostic tests • Interferon γ (QuantiFERON-TB Gold) • Activated specific T-cells (T-SPOT.TB) • Standard under development • Which patients? • How long should it take? • Who provides it? • What do the results mean and who interprets them?

  18. Histopathology • Report within 3 days of receipt • Inform the Microbiology service • Ensure same reporting as for positive microscopy and culture results • Send autopsy samples to Microbiology without formalin!! • [Role of PCR to be determined]

  19. Implementation of standards • Local responsibility • What is done where? • Microscopy; culture; identification • What throughput is needed? • Equipment – cost-effectiveness • Personnel • Maintain skills; CPD; peer review • Named individuals for advice • Back-up and cover • IQC, EQA

  20. Standards for Quality Only do what you can do properly!

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