Evaluating Shared Laboratory Services: Detecting Mycobacterium Tuberculosis Complex and Drug Resistance Using Molecular and Culture-Based Methods

Abstract

Objectives: We explored sharing nucleic acid amplification testing (NAAT) for detection of Mycobacterium tuberculosis complex (MTBC) and molecular and phenotypic drug susceptibility testing between two state public health tuberculosis (TB) laboratories, and evaluated turnaround times and cost-effectiveness.

Methods: From September 1, 2012, to May 30, 2013, the Wisconsin State Laboratory of Hygiene (Wisconsin Lab) submitted specimens to the Microbial Diseases Laboratory of the California Department of Public Health (California Lab) for NAAT and molecular drug susceptibility testing (MDST) by pyrosequencing, and culture-based TB drug susceptibility testing by the BACTEC(TM) MGIT(TM) 960 system.

Results: A total of 182 specimens were referred to the California Lab, and 47 TB cases and 12 drug-resistant cases were identified. The average time for specimen transport was two days, which included one day for processing and packaging in the submitting laboratory. The average turnaround time for NAAT was 0.3 days at the Wisconsin Lab and 3.8 days at the California Lab, including time for specimen transport. Turnaround time for culture-based drug susceptibility testing increased by a median of 16 days when specimens were sent to the California Lab, but MDST results were reported in fewer than four days, a median of 22 days sooner than any culture-based drug susceptibility testing results.

Conclusion: This study revealed advantages and disadvantages associated with sharing services, and identified opportunities for improvement. Referral of specimens resulted in longer turnaround times for mycobacteriology test results and additional costs for transporting specimens. However, specialized testing such as pyrosequencing may not be available in low TB incidence areas, and these rapid results can have positive effects on patient management and TB control.

Figure

Flow chart showing the types of specimens referred from the Wisconsin State Laboratory of Hygiene (WSLH) and the Microbial Diseases Laboratory (MDL) in California, and the progression of testing at each laboratory during the Shared TB Laboratory Services study, September 1, 2012, to May 31, 2013^a