Conclusion

Ordering AFB cultures on specimens from patients who don’t have syndromes consistent with mycobacterial infection may lead to overutilization of AFB cultures. The microbiology laboratory in our system spends about 140 h per week on work dedicated to AFB cultures. If this work were decreased by 50% by setting constraints on ordering tests, the saving would be approximately $116,000 in hourly staff costs alone. These savings don’t include costs for laboratory space, supplies, utilities, or opportunity costs by not doing other tests that could be more beneficial.

Our findings suggest that there could be cost benefit in limiting testing for AFB cultures to reduce inefficient and ineffective use of laboratory resources, as well as opportunity benefit in being able to provide other tests that may be more clinically relevant in our setting. Providing education to medical practitioners about the role of these cultures, especially guidelines on clinical scenarios in which they are not warranted, may help reduce unnecessary time and spending. Other methods to limit testing include automatic blocking in the EMR, ^{Reference Rahamim-Cohen, Valinsky and Beit Or15} eliminating panels of tests, or making ordering more difficult. ^{Reference Conroy, Homsy and Johns16}

A strength of this study lies in the fact that all data analyzed came from real-world clinical settings within the recent past, which provides a substantial sample size with a good distribution across genders and ethnicities. Therefore, the findings of this study provide useful insight into where interventions may be helpful.

There are some limitations to this study. The appropriateness of the cultures ordered was not assessed on all patients. AFB cultures take weeks to provide a definitive result and require clinical correlation as NTMs are common environmental organisms. Follow-up is not available for all of the patients for whom cultures were sent, making it difficult to determine the percentage of tests that were true positive results versus contaminants or colonization.

As expected, most specimens in this study were from pulmonary sources. As with any culture result, clinical correlation is needed to differentiate colonization from infection. Although there has been an increase in infection due to NTMs, ^{Reference Winthrop, Marras, Adjemian, Zhang, Wang and Zhang18} this would not account for all positive results obtained. It is likely that at least half of the NTMs obtained from pulmonary specimens represented colonization or contamination versus being true pathogens. Our results likely underestimate the magnitude of the positive culture results that were not pathogenic. In addition to excess costs and laboratory resources being used to identify bacteria that may not be clinically relevant, there are potential patient costs in terms of unnecessary exposure to antimicrobial therapy when it is difficult to decide whether an organism may be a pathogen and providers opt to treat it out of caution.

Implementing laboratory criteria for accepting specimens for AFB cultures and reviewing AFB cultures prior to having them undergo further testing for identification and sensitivity could reduce costs for the microbiology laboratory and liberate personnel to perform other clinical tests.