Use of recommended laboratory testing methods among patients with tuberculosis in California

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.

Laboratory reporting of tuberculosis test results and patient treatment initiation in California

Prompt laboratory reporting of tuberculosis (TB) test results is necessary for TB control. To understand the extent of and factors contributing to laboratory reporting delays and the impact of reporting delays on initiation of treatment of TB patients, we analyzed data from 300 consecutive culture-positive TB cases reported in four California counties in 1998. Laboratory reporting to the specimen submitter was delayed for 26.9% of smear-positive patients and 46.8% of smear-negative patients. Delays were associated with the type of laboratory that performed the testing and with delayed transport of specimens. Referral laboratories (public health and commercial) had longer median reporting time frames than hospital and health maintenance organization laboratories. Among patients whose treatment was not started until specimens were collected, those with delayed laboratory reporting were more likely to have delayed treatment than patients with no laboratory reporting delays (odds ratio [OR] of 3.9 and 95% confidence interval [CI] of 1.6 to 9.7 for smear-positive patients and OR of 13.1 and CI of 5.3 to 32.2 for smear-negative patients). This relation remained after adjustment in a multivariate model for other factors associated with treatment delays (adjusted OR of 25.64 and CI of 7.81 to 83.33 for smear-negative patients). These findings emphasize the need to reduce times of specimen transfer between institutions and to ensure rapid communication among laboratories, health care providers, and health departments serving TB patients.