Microscopic observation drug susceptibility assay for tuberculosis screening before isoniazid preventive therapy in HIV-infected persons.
BACKGROUND
Active tuberculosis (TB) must be excluded before initiating isoniazid preventive therapy (IPT) in persons infected with human immunodeficiency virus (HIV), but currently used screening strategies have poor sensitivity and specificity and high patient attrition rates. Liquid TB culture is now recommended for the detection of Mycobacterium tuberculosis in individuals suspected of having TB. This study compared the efficacy, effectiveness, and speed of the microscopic observation drug susceptibility (MODS) assay with currently used strategies for TB screening before IPT in HIV-infected persons.


METHODS
A total of 471 HIV-infected IPT candidates at 3 hospitals in Lima, Peru, were enrolled in a prospective comparison of TB screening strategies, including laboratory, clinical, and radiographic assessments.


RESULTS
Of 435 patients who provided 2 sputum samples, M. tuberculosis was detected in 27 (6.2%) by MODS culture, 22 (5.1%) by Lowenstein-Jensen culture, and 7 (1.6%) by smear. Of patients with any positive microbiological test result, a MODS culture was positive in 96% by 14 days and 100% by 21 days. The MODS culture simultaneously detected multidrug-resistant TB in 2 patients. Screening strategies involving combinations of clinical assessment, chest radiograph, and sputum smear were less effective than 2 liquid TB cultures in accurately diagnosing and excluding TB (P<.01). Screening strategies that included nonculture tests had poor sensitivity and specificity.


CONCLUSIONS
MODS culture identified and reliably excluded cases of pulmonary TB more accurately than other screening strategies, while providing results significantly faster than Lowenstein-Jensen culture. Streamlining of the ruling out of TB through the use of liquid culture-based strategies could help facilitate the massive up-scaling of IPT required to reduce HIV and TB morbidity and mortality.
Reddy
Krishna P
KP
Laboratorio de Investigación de Enfermedades Infecciosas, Universidad Peruana Cayetano Heredia, Lima, Peru. kreddy@post.harvard.edu
Brady
Mark F
MF
Gilman
Robert H
RH
Coronel
Jorge
J
Navincopa
Marcos
M
Ticona
Eduardo
E
Chavez
Gonzalo
G
Sánchez
Eduardo
E
Rojas
Christian
C
Solari
Lely
L
Valencia
Jorge
J
Pinedo
Yvett
Y
Benites
Carlos
C
Friedland
Jon S
JS
Moore
David A J
DA
D000328:Adult; D000995:Antitubercular Agents / Q000008:administration & dosage*; D015373:Bacterial Typing Techniques / Q000191:economics / Q000379:methods*; D016009:Chi-Square Distribution; D024881:Drug Resistance, Bacterial; D005260:Female; D015658:HIV Infections / Q000382:microbiology*; D006801:Humans; D007538:Isoniazid / Q000008:administration & dosage*; D008297:Male; D008826:Microbial Sensitivity Tests / Q000191:economics / Q000379:methods*; D008853:Microscopy / Q000379:methods; D009169:Mycobacterium tuberculosis / Q000187:drug effects*; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D013048:Specimen Handling; D013183:Sputum / Q000382:microbiology; D013997:Time Factors; D014376:Tuberculosis / Q000175:diagnosis* / Q000382:microbiology / Q000517:prevention & control / Q000821:virology
D000995:Antitubercular Agents; D007538:Isoniazid