The MODS Assay for Detection of TB and TB Drug Resistance: A Multi-center Study

Transcription

1 The MODS Assay for Detection of TB and TB Drug Resistance: A Multi-center Study microscopic observation drug susceptibility Susan E. Dorman, MD Johns Hopkins University Afranio L. Kritski, MD, PhD Federal University of Rio de Janeiro June 1, 2006

2 Rio de Janeiro ICIDR Program Community randomized trial of 2 TB prevention strategies Randomized trial of two TB chemoprevention strategies Novel diagnostic techniques for TB and TB drug resistance

3 Rio de Janeiro ICIDR Program Community randomized trial of 2 TB prevention strategies Randomized trial of two TB chemoprevention strategies Novel diagnostic techniques for MODS TB and TB drug resistance Study

4 What is MODS? microscopic observation drug susceptibility Pioneered by Robert Gilman in Peru Liquid culture method for detection of M. tuberculosis Microscopic detection of bacterial cording that is characteristic for M. tuberculosis Can be adapted for drug susceptibility testing Relatively simple, relatively inexpensive, no radioactivity

5 What is MODS? MODS assay culture plate cording of M. tuberculosis

6 Study Objectives To evaluate sensitivity and specificity of MODS for detection of M. tuberculosis in respiratory specimens from pulmonary TB suspects in disease endemic settings To evaluate the time to growth for M. tuberculosis in MODS versus Lowenstein-Jensen, and versus MGIT 960 To evaluate the sensitivity and specificity of MODS for direct detection of isoniazid and rifampin drug resistance At study sites, to increase capacity to evaluate new TB diagnostic tests using Good Laboratory Practices, and to facilitate South-South collaboration

7 Study Design Prospective, multicenter Federal University of Rio de Janeiro, Brazil Instituto Nacional del Torax, Honduras Respiratory specimens obtained from pulmonary TB suspects (~ 70% outpatients) Comparators Clinical diagnosis of TB (includes LJ culture results) Companion Lowenstein-Jensen culture Sample size 1655 respiratory specimens

8 Study Scheme respiratory specimen smear microscopy Lowenstein- Jensen culture MODS culture Direct MODS DST isoniazid rifampin MGIT culture Indirect LJ DST isoniazid rifampin

9 Characteristics of 854 Study Subjects (adult pulmonary TB suspects) Characteristic # % Brazil Honduras Male Female Type of Subject New TB suspect Suspected TB relapse Suspected TB treatment failure Suspected TB treatment defaulter HIV positive HIV negative HIV not tested

10 Characteristics of 1639 Study Specimens Characteristic # % Brazil Honduras Expectorated sputum Induced sputum Bronchoalveolar lavage/bronch wash

11 Overall Results (by specimen) # % AFB smear positive LJ culture positive for M. tuberculosis MODS culture positive for M. tuberculosis LJ culture positive for NTM

12 Proportions of contaminated cultures for Lowenstein-Jensen and MODS % contaminated p < % LJ MODS

13 Performance characteristics of MODS for detection of TB TB Diagnosis Companion LJ Sensitivity (%) 97.5* 96.5 Specificity (%) PPV (%) NPV (%) Agreement (%) N/A 94.2 *LJ sensitivity 98.9% difference 1.4%, 95% CI -0.5 to 2.7; p=0.27

14 Time to growth for culture positive specimens, by culture method Days to growth of M. tuberculosis For LJ and MODS: N=657 specimens p < For MGIT: N=64 specimens p = 0.16 for MODS vs MGIT LJ MODS MGIT

15 Time to growth, by culture method and smear microscopy status % positive for growth Smear negative, N=135 Smear positive, N=522 LJ, smear negative MODS, smear negative LJ, smear positive MODS, smear positive Days to M. tuberculosis grow th

16 Overall Drug Susceptibility Test Results Lowenstein-Jensen Result # % Susceptible to INH and RIF INH resistant RIF susceptible INH susceptible RIF resistant Resistant to INH and RIF N = 188 study subjects having risk factor(s) for drug resistant TB

17 Performance characteristics of MODS for detection of drug resistance Isoniazid Rifampin Sensitivity (%) Specificity (%) PPV (%) NPV (%) Agreement (%) Comparator: Lowenstein-Jensen N=188 subjects with risk factor(s), and positive LJ and MODS cx

18 Summary For diagnosis of pulmonary TB, MODS has good sensitivity, which is similar to that of LJ MODS has an acceptable contamination rate Time to detection of MODS growth is about one-third that of LJ, and similar to MGIT MODS identifies as TB some non-tuberculous mycobacteria MODS is sensitive for detection of isoniazid or rifampin resistance MODS indicates as resistant some cultures that are susceptible to INH or rifampin MODS performed similarly at both study sites

19 Conclusions Rapidity of growth and low contamination rates make MODS an attractive platform Inability to accurately differentiate M. tuberculosis from some non-tuberculous mycobacteria may be problematic in some settings Good sensitivity, high NPV, and short turnaround time of MODS for direct detection of INH and/or RIF resistance might make MODS suitable as a screening test in order to prioritize isolates for subsequent confirmatory indirect testing using conventional methods

20 Acknowledgements Federal Univ of Rio de Janeiro Fernanda Mello Anna Grazia Marsico Leo Pessoa Monica Andrade Leila Fonseca Afranio Kritski Johns Hopkins University Richard Chaisson National Thorax Institute, Honduras Ada Pavon Carlos Alvarado-Galvez Senia Rosales Melly Perez University of Alabama Mayra Arias Michael Kimerling NIH / DMID USAID

21 Laboratory Methods Respiratory specimens were obtained from TB suspects undergoing evaluation for TB Specimens were processed using a NALC-NaOH method of decontamination/mucolysis LJ culture and indirect drug susceptibility testing for INH and RIF were performed according to published standards 0.2 ml each processed respiratory specimen was inoculated into 1 ml of MODS/PANTA 7H9-based liquid media, and into 1 ml of MODS/PANTA medium containing para-nitrobenzoic acid For MODS direct drug susceptibility testing, INH concentration was 0.1 ug/ml, and RIF concentration was 2.0 ug/ml. MODS wells were observed microscopically under 40X magnification at a frequency of twice weekly For LJ cultures, standard biochemical tests were used to determine mycobacterial species For MODS cultures, cording morphology and absence of growth in PNB were considered diagnostic of M. tuberculosis