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
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
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
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
What is MODS? MODS assay culture plate cording of M. tuberculosis
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
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
Study Scheme respiratory specimen smear microscopy Lowenstein- Jensen culture MODS culture Direct MODS DST isoniazid rifampin MGIT culture Indirect LJ DST isoniazid rifampin
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 559 295 491 363 521 178 113 42 102 297 455 65.5 34.5 57.5 42.5 61.0 20.8 13.2 4.9 11.9 34.8 53.3
Characteristics of 1639 Study Specimens Characteristic # % Brazil Honduras 977 662 59.6 40.4 Expectorated sputum Induced sputum Bronchoalveolar lavage/bronch wash 1353 237 49 82.5 14.5 3.0
Overall Results (by specimen) # % AFB smear positive 594 36.2 LJ culture positive for M. tuberculosis MODS culture positive for M. tuberculosis 681 41.5 728 44.4 LJ culture positive for NTM 17 2.0
Proportions of contaminated cultures for Lowenstein-Jensen and MODS % contaminated 10 9 8 7 6 5 4 3 2 1 0 p < 0.001 5% LJ MODS
Performance characteristics of MODS for detection of TB TB Diagnosis Companion LJ Sensitivity (%) 97.5* 96.5 Specificity (%) 95.1 92.6 PPV (%) 93.6 90.2 NPV (%) 98.1 97.4 Agreement (%) N/A 94.2 *LJ sensitivity 98.9% difference 1.4%, 95% CI -0.5 to 2.7; p=0.27
Time to growth for culture positive specimens, by culture method Days to growth of M. tuberculosis 55 50 45 40 35 30 25 20 15 10 5 For LJ and MODS: N=657 specimens p < 0.0001 For MGIT: N=64 specimens p = 0.16 for MODS vs MGIT LJ MODS MGIT
Time to growth, by culture method and smear microscopy status 100 90 % positive for growth 80 70 60 50 40 30 20 10 Smear negative, N=135 Smear positive, N=522 LJ, smear negative MODS, smear negative LJ, smear positive MODS, smear positive 0 0 5 10 15 20 25 30 35 40 45 50 55 Days to M. tuberculosis grow th
Overall Drug Susceptibility Test Results Lowenstein-Jensen Result # % Susceptible to INH and RIF 69 36.7 INH resistant 35 18.6 RIF susceptible INH susceptible 13 6.9 RIF resistant Resistant to INH and RIF 71 37.8 N = 188 study subjects having risk factor(s) for drug resistant TB
Performance characteristics of MODS for detection of drug resistance Isoniazid Rifampin Sensitivity (%) 97.2 96.4 Specificity (%) 89.0 86.5 PPV (%) 92.0 85.3 NPV (%) 96.1 96.8 Agreement (%) 93.6 91.0 Comparator: Lowenstein-Jensen N=188 subjects with risk factor(s), and positive LJ and MODS cx
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
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
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
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