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

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Presentation on theme: "Standards for Laboratory Diagnosis of Tuberculosis Professor Brian I. Duerden Inspector of Microbiology and Infection Control, Department of Health."— Presentation transcript:

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 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 Standards to cover 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

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

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11 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

12 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

13 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

14 Susceptibility testing Complete within 30 days of initial receipt of clinical sample for primary agents –Isoniazid, rifampicin, pyrazinamide, ethambutol Takes 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

15 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

16 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

17 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

18 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?

19 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]

20 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

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22 Standards for Quality Only do what you can do properly!


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