CULTURE OR PCR WHAT IS

Transcription

1 CULTURE OR PCR WHAT IS BEST FOR AFRICA? Peter R Mason BRTI

2 TB IN AFRICA GLOBAL 9 MILLION NEW CASES/YR 1.5 MILLION TB DEATHS AFRICA 95% TB DEATHS IN LMIC 9/22 HIGH BURDEN COUNTRIES IN AFRICA STRONG LINK BETWEEN HIV AND TB

3 TB OR NOT TB CLASSICAL DIAGNOSTICS SYMPTOMS CHEST X-RAY MICROSCOPY ZN CULTURE? SOLID

4 WHAT DO WE MEAN BY BEST? RELIABILITY SENSITIVITY SPECIFICITY ACCESSIBILITY POINT OF CARE TIME TO DETECTION COST AFFORDABLE IN SETTING OF HIGH HIV BURDEN POOR INFRASTRUCTURE

5 RELIABILITY SENSITIVITY DETECT ALL CASES SPECIFICITY DETECTED CASES REALLY ARE TB

6 WHAT ARE THE CONSEQUENCES? LOW SENSITIVITY CASES REMAIN UNDIAGNOSED INFECTIOUS TO OTHERS HIGH RISK OF MORTALITY LOW SPECIFICITY OVERUSE OF TB DRUGS IN COMMUNITY INCREASED RISK OF EMERGENCE OF MDR-TB

7 WHAT IS BEST? HIGH SENSITIVITY RAPID AFFORDABLE ACCESSIBLE DOTS CAN COMPENSATE FOR LOW SPECIFICITY

8 HOW TO MEASURE AFFORDABILITY? COST OF MATERIALS INCL. COST OF REJECTED/FAILED MEDIA COST OF PERSONNEL SPECIALISED TRAINING COST OF INFRASTRUCTURE LABORATORY EQUIPMENT SAFETY QUALITY COST PER CASE DETECTED WHICH SPECIMEN COST OF COLLECTION COST OF EXAMINATION COST PER PATIENT ON Rx INCLUDING DEFAULTERS

9 ESTIMATED COSTS (WHO) LABORATORY INFRASTRUCTURE $200,000 CONSUMABLES >$25 PER SPECIMEN FOR CULTURE TRAINING $20,000 PER PERSON EQA $5,000 PER YEAR SALARIES FOR MIN. 2 LAB STAFF

10 HOW DO WE MEASURE ACCESSIBILITY? MOST TB CASES IN POORER COMMUNITIES ACCESS TO DIAGNOSTIC FACILITY SIMPLER THE BETTER

11 WHAT ARE OUR OPTIONS? CLINICAL + CXR MICROSCOPY CULTURE MOLECULAR OTHER

12 HOW GOOD ARE STANDARD DIAGNOSTIC SCREENS? ACTG STUDY 80 (Swindells et al, IJ TB Lung Dis, 2013) Symptom-based screening with smear microscopy was insufficiently sensitive. More sensitive diagnostic testing is required for HIVinfected patients SOC screen Sensitivity Specifiity

13 DELAY IN ACCESS TO TREATMENT MEDIAN DAYS DELAY PATIENT 30 (20-60) DIAGNOSTIC 7 (3-28) TREATMENT 3 (1-4) TOTAL 45 (35-70) Asefa A, Teshome W. PLoS ONE 2014

14 MICROSCOPY ADVANTAGES RAPID TRAINING HIGH SPECIFICITY (85-95%) LOW COST (<$1) ACCESSIBLE DISADVANTAGES LOW SENSITIVITY (35-75%) ESP. PAUCIBACILLARY ESP. IN HIV HIGH OPERATOR VARIANCE LABOUR INTENSIVE LOW THROUGHPUT

15 HOW CAN WE IMPROVE MICROSCOPY? SPECIMEN AND PROCESSING STAINS READING

16 SPECIMENS STANDARD SPOT SPUTUM MORNING SPUTUM ALTERNATIVES SPUTUM INDUCTION USING LIQUID CULTURE AS GOLD STANDARD DIAGNOSTIC YIELD OF INDUCTION +0.7% ( %) AGAINST SPOT +4.7% ( %) AGAINST MORNING Geldenhuys et al. PLoS ONE 2014

17 STAINS FLUORESCENCE INCR. SENSITIVITY BY UP TO 10% REDUCES TIME TO DETECTION REDUCES WORK LOAD INCREASES THROUGHPUT LED MICROSCOPY BATTERY POWER LONG LIFE USE IN DAYLIGHT COMMUNITY DIAGNOSIS

18 MICROSCOPY AFFORDABLE ACCESSIBLE RAPID Sens (%) BUT LOW SENSITIVITY EVEN WITH MODIFICATIONS, ESP. IN HIV CO-INFECTION (Alfred et al, BMJ Open 2014) Direct ZN Direct Fluor LED

19 CULTURE STANDARD APPROACH IN BACTERIOLOGY BUT LONG DIVISION TIME (20hrs) SLOW GROWTH SAFETY

20 STANDARD CULTURE SOLID MEDIA EGG-BASED e.g. LOWENSTEIN JENSEN SENSITIVITY 85-95% SPECIFICITY % MATERIAL COST $5-12

21 LJ CULTURE ADVANTAGES HIGH SENSITIVITY IN CLINICAL SPECIMENS ( bacteria/ml) DRUG SENSITIVITY PERMANENT DISADVANTAGES LABOUR INTENSIVE LOW THROUGHPUT SLOW GROWTH 6-8 WEEKS SAFETY ISSUES SPECIAL INFRASTRUCTURE & TRAINING

22 ALTERNATIVES MGIT MODS

23 BACTEC MGIT (MYCOBACTERIUM GROWTH INDICATOR TUBE) LIQUID CULTURE (MIDDLEBROOK 7H9 BROTH + ENHANCEMENT + ANTIBIOTIC) FLOURESCENT DETECTION OF BACTERIAL GROWTH AUTOMATED OR MANUAL DETERMINATION OF FLUORESENCE UNDER UV

24 BACTEC MGIT INCREASED DIAGNOSTIC YIELD LJ 23% MGIT 30% MGIT smear - MGIT-smear + Days (Chihota et al, IJ TB Lung Dis, 2010) LJ DECREASED TIME TO DETECTION

25 MODS (MICROSCOPICALLY OBSERVED DRUG SUSCEPTIBILITY) THIN LAYER SOLID MEDIA GROWTH DETECTED BY MICROSCOPY ADAPTED TO DRUG SUSCEPTIBILITY ASSAY

26 MODS ZIMBABWE (vs MGIT) SENSITIVITY 85% (69-95%) SPECIFICITY 93% (84-98%) MEDIAN TTD 7 days (MGIT 12d; LJ-28d) Makamure et al. PLoS ONE 2013

27 MODS IN HIV SETTINGS ALL CULTURES SENSITIVITY 88% (86-90%) SPECIFICITY 100% (95-100%) MEDIAN TTD 8 days SMEAR NEGATIVE SENSITIVITY 88% (86-90%) SPECIFICITY 98% (96-99%) Systematic Review: Wikman-Ingesen (Mozambique) BMC Inf Dis 2014

28 MODS KITS TTD Specifity Sensitivity

29 MOLECULAR METHODS IN HOUSE PCR MOSTLY BASED ON IS6110 LARGE INTER-LABORATORY VARIABILITY GENE XPERT MTB/RIF AUTOMATED RAPID SAFE RESISTANCE TO RIFAMPICIN

30 GENE XPERT MTB/RIF

31 RELIABILITY 18 STUDIES > 10,000 SPECIMENS >3,000 TB POSITIVE >6,000 SMEAR & CULTURE NEGATIVE % Average sensitivity for diagnosis of TB: 90.4% Average specificity for diagnosis of TB : 98.4% Chang et al, J Infection Sensitivity Specificity

32 IN TERTIARY CARE SETTINGS ZAMBIA COMPARED WITH CULTURE POSITIVE O Grady et al. Clin Inf Dis % Sensitivity Specificity Sputum -ve

33 IN PRIMARY CARE SETTINGS MULTI-CENTRE STUDY IN SOUTHERN AFRICA COMPARING MTB/Rif & FM AT PoC Sensitivity Specificity Theron et al, Lancet, 2014

34 ADVANTAGE OF PoC TESTING SAME DAY DIAGNOSIS 40 SAME DAY TREATMENT INITIATION 20 MTB/Rif FM Theron et al, Lancet, Same day DX Same day Rx

35 GENE XPERT MTB/Rif ADVANTAGES RAPID SAME DAY RESULT ACCESSIBLE CAN BE USED AT POINT OF CARE RELIABLE HIGH SENSITIVITY & SPECIFICITY DISADVANTAGES COST ANNUAL MAINTENANCE SHELF LIFE POWER SUPPLY

36 WHEN TO USE GXP MTB/Rif? SYSTEMATIC REVIEW 27 STUDIES REPLACE ZN ADD ON TO ZN (smear negatives) Sensitivity Specificity Steingard etal, Cochrane DB Sys Rev 2014

37 WHO RECOMMENDATION (2011) GXP MTB/Rif DOES NOT PRECLUDE THE NEED FOR OTHER ASSAYS MICROSCOPY & CULTURE HAVE A ROLE TO PLAY GXP MTB/Rif CAN REPLACE MICROSCOPY HIGH RISK OF HIV HIGH RISK OF MDR IN OTHER SITUATIONS ADD ON IS MORE APPROPRIATE

38 OTHERS NOVEL APPROACHES RATS (CRICETOMYS) IMMUNOLOGICAL APPROACHES INTERFERON GAMMA LIPOARABINOMANNAN NEW ANTIGENS

39 INTERFERON GAMMA (IGRA) USEFUL FOR DETECTION OF LATENT TB LESS VALUE IN DETECTION OF ACTIVE TB ESP. IN HIV LOWER SPECIFICITY THAN OTHERS

40 LAM URINARY EXCRETION OF LAM HIGHLY VARIABLE FINDINGS SENSITIVITY 6% TO 81% SENSITIVITY USUALLY HIGHEST IN HIV-INFECTED PATIENTS WITH LOW CD4 COUNTS

41 NEW ANTIGENS IMMUNODOMINANT PEPTIDE ANTIGENS USING DIFFERENT ANTIGEN COMBINATIONS, SENSITIVITY & SPECIFICITY >90% LATERAL FLOW ASSAYS UNDER DEVELOPMENT Gonzalez et al, PLoS One, 2014

42 THE FUTURE?