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Explore the latest technology in tuberculosis testing, including CDC recommendations for TB labs, clinical significance of rapid testing, and detailed procedures for TB laboratory processing. Get ready to process specimens with precision and accuracy, utilizing innovative methods for TB detection.
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LABORATORYDIAGNOSTICTOOLS Presented by Jason A. Lee 1999
TB is a Deadly Infectious Disease Worldwide • 1.7 billion people infected with TB • 10% will develop active disease • 8 million new cases/year • 3.3 million deaths/year
CDC RECOMMENDATIONS FOR TB LABORATORIES • Report AFB results within 24 hours of receipt in Lab Fluorescent stain (PHL confirms with Kinyoun stain) • Detect growth in liquid medium within 10 daysPHL uses MB/BacT system and L - J - slants • Identify MTB isolates within 14-21 days of receipt in Lab Mycolic acid patterns by HPLC or nucleic acid probes Con’t
CDC RECOMMENDATIONS FOR TB LABORATORIES (con’t) • Determine susceptibility of new MTB isolates to primary drugs and report results within 21-28 days of receipt in Lab. When Multi-drug resistance is found, test isolate to another methodology for confirmation. Isoniazid, rifampin, streptomycin, ethambutol and pyrazinamide • Submit all isolates to a fingerprinting Lab This helps to identify cross-contamination and provides EPI information
Clinical Significance ofRapid TB Testing • Isolate patients to prevent spread of disease • Treatment decisions: Is it MTB or MOTT? • Reduce health care cost: • Cost of patient isolation/treatment • Cost of further spread of disease
AVERAGE TB LABORATORY Sputum or Other Sample Na0H - NALC Centrifugation Sediment Liquid Culture Solid Culture Acid- Fast Microscopy Report within 24 hrs Identify - HPLC or Probes No Growth Report within 6 wks Report within 21 days MTB MOTT Drug Susceptibility Report within 28 days
PHL - TB LABORATORY Sputum or Other Sample Na0H - NALC Centrifugation Sediment BacT (MB/BacT LJ AFB Fluorochrome Confirmed by Kinyoun Reportwithin 24 hrs No Growth Report Within 6 wks Growth New Patients Not on Treatment Amplified Test Gen Probe Identify by Mycolic Acid Pattern using HPLC or by Nucleic Acid Probes. Emergency Reports can be reported within 6hrs
MTB MOTT Results Reported 7 - 21 days All isolates Are Sent For Fingerprinting Drug Susceptibilities BacTec Conventional Plate Susceptibilities Performed for Confirmation Non - resistant Resistant Results Reported 21 - 35 days and decreasing)
THE PRINCIPLE OF GROWTH DETECTION FromGreenTo Yellow CO2 Sensor
THE PATTERNS FOR MOTTs M. fortuitum M. chelonae M. terrae complex (M. nonchromogenium M. gordonae
Amplified Mycobacterium Tuberculosis Direct (MTD) Assay • Amplified molecular diagnostic assay detects M. tuberculosis directly in sputum samples in 3 hours • Utilizes a Transcription-Mediated Amplification system (TMA) • Transcription of RNA amplicon from ribosomal RNA targets • Amplicon is detected by DNA probes in the Hybridization Protection Assay format (HPA) • Single tube format
Amplified MTD Clinical Utility Algorithm AFB Smears Positive Samples + - MTD Test MTD-Positive 100% PPV for TB TB Unlikely 86.3% NPV, MOTT Likely Verify MOTT by Alternate Testing Method Repeat MTD Test with New Specimen Test for Inhibition Positive M. tuberculosis Identification Confirmation with Culture
AMPLIFICATION TEST PERFORMED BY THE PHL * This sample was digested by the submitter, referred to the PHL, we digested it again!
Amplified Test Reliability Culture - + TP 43 FP 1 + Gen-Probe Amplified Test FN 0 TN 31 - Sensitivity = TP x 100 = 100% TP+ FN Specificity = TN x 100 = 97% TP+ FN TPx 100 = 98% Positive Predictive Value = TP+ FP Negative Predictive Value = TN x 100 = 100% TP+ FN