Reduction in turnaround time for laboratory diagnosis of pulmonary tuberculosis by routine use of a nucleic acid amplification test.
Every first diagnostic specimen from suspected patients with pulmonary TB was tested by a nucleic acid amplification test (NAAT) to determine the reduction in turnaround time (TAT) for detecting Mycobacterium tuberculosis (MTB) that was possible under normal laboratory operating conditions. NAAT (Gen-Probe Mycobacterium tuberculosis Direct Testtrade mark) was performed on the first specimen and liquid culture (BACTEC 460), solid culture (Lowenstein-Jensen [LJ] agar and selective 7H11 [7H11S] agar), and fluorescent acid-fast bacilli (AFB) smear were performed on all 3 specimens from each patient. Eighty-one (10.2%) of 797 patients tested were diagnosed with pulmonary TB. The sensitivity of NAAT, BACTEC, LJ, 7H11S, and smear for the first specimen was 90%, 85%, 67%, 53%, and 58%, respectively, whereas the sensitivity for the series of 3 specimens was 90%, 95%, 74%, 74%, and 70%, respectively. Positive predictive value was 100% for all tests except AFB smear, which was 79%. The time to detect 75% of all TB cases was 4 days for NAAT and 21 days for liquid culture; other tests had a sensitivity of less than 75%. Identification and testing every first diagnostic specimen by NAAT has the potential to reduce the overall TAT for laboratory TB diagnosis by approximately 2 weeks.
Moore
Douglas F
DF
Public Health Laboratory, Orange County Health Care Agency, Santa Ana, CA 92706, USA. dmoore@hca.co.orange.ca.us
Guzman
Joseph A
JA
Mikhail
Lydia T
LT
D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics*; D006801:Humans; D009169:Mycobacterium tuberculosis / Q000235:genetics* / Q000302:isolation & purification; D021141:Nucleic Acid Amplification Techniques / Q000379:methods*; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D013997:Time Factors; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000382:microbiology
D004269:DNA, Bacterial