Knowledge at what cost? An audit of the utility of panfungal PCR performed on bronchoalveolar lavage fluid specimens at a tertiary mycology laboratory

Abstract

The diagnostic utility and costs of panfungal PCR assays for invasive fungal disease (IFD) from bronchoalveolar lavage fluid (BALF) specimens are incompletely defined. In a retrospective audit, panfungal PCR results from 2014-2018 were matched with information on request forms and the registrar/microbiologist diary of clinical liaison. Identification of a single fungus other than a commensal was considered potentially clinically significant, and assessed for clinical relevance. Of 1002 specimens tested, an estimated 90% were requested in patients without clinical suspicion of IFD. There were 530 (52.9%) PCR-positive results of which 485/530 (91.5%) identified multiple fungal species or commensal fungi; 45 (8.5%) were clinically significant but only in 12 (1.2%) was panfungal PCR the sole diagnostic test leading to IFD diagnosis, all in immunocompromised patients with clinical suspicion of IFD. Costs of panfungal PCR tests averaged AUD 133 per test, or AUD 26,767/annum. However, the average cost-per-diagnosis achieved was AUD 15,978/annum. Limiting testing to patients at risk and with clinical suspicion of IFD, may save over AUD 13,383/annum (assuming 50-90% reduction in testing). The value-added utility of panfungal PCR on BALF is 1.2% (12/1002). We have since introduced pre-analytical stewardship limiting routine panfungal PCR testing of BALF to high-risk patients in our hospital.

Keywords: Panfungal PCR; bronchoalveolar lavage fluid; diagnostic stewardship; fungi.