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Journal of Clinical Microbiology, Apr 1996, 860-865, Vol 34, No. 4
JA Down, MA O'Connell, MS Dey, AH Walters, DR Howard, MC Little, WE Keating, P Zwadyk Jr, PD Haaland, DA McLaurin 3rd and G Cole
A total of 294 clinical respiratory specimens, including 75 with
culture-positive results, were tested for the presence of Mycobacterium
tuberculosis by strand displacement amplification (SDA) of DNA. A region of
the IS6110 insertion element and an internal control sequence were
amplified and then detected by a chemiluminescence assay. Receiver
operator-characteristic curves were used to evaluate three methods for
declaring specimens positive for M. tuberculosis. By the preferred method,
SDA chemiluminescence results were converted to theoretical numbers of M.
tuberculosis organisms. A positive threshold (PT) value, above which 95% of
the SDA results were judged to be M. tuberculosis positive (sensitivity =
95%), was found to be 2.4 M. tuberculosis organisms per SDA reaction. The
analogous PT value for 95% sensitivity on smear-positive specimens was 3.6
M. tuberculosis organisms per reaction. The PT of 2.4 M. tuberculosis
organisms per reaction detected 100% of culture-positive, smear-positive
specimens (sensitivity = 100%), while 95% sensitivity was achieved with a
PT of 15.5 M. tuberculosis organisms per reaction. Specificities, which
were calculated with respect to culture- and smear-negative specimens,
ranged from 96% at a PT of 15.5 M. tuberculosis organisms to 84% at a PT of
2.4 M. tuberculosis organisms per reaction. The M. tuberculosis- negative
specimens were also segregated according to whether the patients received
antituberculosis chemotherapy. SDA specificity ranged from 90% (PT = 2.4 M.
tuberculosis organisms) to 98% (PT = 15.5 M. tuberculosis organisms) for
the M. tuberculosis-negative specimens from patients who had not received
chemotherapy. SDA specificity in the M. tuberculosis-negative specimens
from patients who received chemotherapy was lower (85 to 94%). This study
represents the first large-scale demonstration of M. tuberculosis detection
in clinical sputum specimens by isothermal DNA amplification with SDA.
Copyright © 1996 by the American Society for Microbiology. All rights reserved.
Detection of Mycobacterium tuberculosis in respiratory specimens by strand displacement amplification of DNA
Becton Dickinson Research Center, Research Triangle Park, North Carolina 27709-2016, USA. Down@bdrc.bd.com
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