Study objective: To evaluate the usefulness of the
Gen-Probe Amplified Mycobacterium Tuberculosis Direct Test (AMTDT;
Gen-Probe; San Diego, CA) in predicting the results of cultures in
routine laboratory analysis of a patient population with a high
incidence of tuberculosis (TB).
hundred ten patients suspected of pulmonary mycobacterial infection or
receiving antituberculous chemotherapy, accrued between 1996 and
Setting: Tertiary-care facility located in
Design: We retrospectively compared
the AMTDT results with the results of cultures. AMTDT results were also
compared with those of acid-fast bacilli (AFB) staining of the same
specimens. The study included 360 respiratory specimens from 310
patients collected between 1996 and 1997. In 1996, we used the initial
version of AMTDT (50 μL of sediment); in 1997, we used the new
version of AMTDT (450 μL of sediment).
Compared with cultures, AMTDT and AFB staining had sensitivities of
87.2% and 68.4%, and specificities of 70.0% and 89.7%,
respectively. When AMTDT and AFB staining were both positive, the
sensitivity and specificity were 89.3% and 96.9%, respectively. When
AMTDT and AFB staining were in disagreement, the sensitivity and
specificity of AMTDT were 81.8% and 18.1%, respectively.
Conclusion: We conclude that when AMTDT is used to predict
culture outcome, the results should be evaluated in conjunction with
AFB staining results before making decisions about TB