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Journal of Clinical Microbiology, 09 1997, 2424-2426, Vol 35, No. 9
E Tortoli, F Lavinia and MT Simonetti
Direct detection of Mycobacterium tuberculosis by means of a commercial
ligase chain reaction DNA amplification method (LCx M. tuberculosis; Abbott
Diagnostics Division, Abbott Park, Ill.) was investigated with 511
(including 147 extrarespiratory) specimens collected from 358 patients. LCx
results were compared with standard microbiological data, and conflicting
cases were resolved according to the final clinical diagnosis. M.
tuberculosis was detected in 45 of 358 subjects by means of the LCx test.
The test was negative for all 30 specimens with mycobacteria other than M.
tuberculosis. The sensitivity, specificity, and positive and negative
predictive values for the LCx test, compared with culture results, were
93.90, 92.31, 70.00, and 98.75%, respectively; these values rose in
resolved cases to 95.53, 99.25, 97.27, and 98.75%, respectively. With
respiratory specimens, for which the LCx system is licensed, the
sensitivity reached 98.97%. In patients with a final clinical diagnosis of
tuberculosis the sensitivity of the LCx system was 89.36% compared to
82.98% for cultures and 78.72% for microscopy. We conclude that the LCx
test is user friendly, rapid, fairly sensitive, and highly specific. It can
also be effectively used on extrapulmonary specimens provided possible
false-negative results are taken into account. However, the use of LCx test
appears to be less appropriate for the monitoring of antituberculosis
therapy, as the majority of samples from treated tuberculosis patients gave
consistently positive results, despite the sterilization of cultures.
Copyright © 1997 by the American Society for Microbiology. All rights reserved.
Evaluation of a commercial ligase chain reaction kit (Abbott LCx) for direct detection of Mycobacterium tuberculosis in pulmonary and extrapulmonary specimens
Laboratorio di Microbiologia e Virologia, Ospedale di Careggi, Firenze, Italy. tortoli@dada.it
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