Utility of Turbidimetric Beta-D-Glucan in Lung Transplant Recipients

Abstract

<h3>Purpose</h3> Beta-D-Glucan (BDG) is a cell wall polysaccharide and its detection in serum can be indicative of fungal infection. Evidence for BDG testing in solid organ transplantation has been derived from data using a colorimetric assay. We introduced a turbidimetric assay for BDG (Wako) into our center and assessed its utility in the diagnosis of fungal infections in lung transplant recipients. Furthermore, BDG can be used as an antimicrobial stewardship tool if results are available promptly, as a high negative predictive value can give clinicians confidence in stopping or avoiding empiric antifungal therapy. <h3>Methods</h3> Data were collected on 115 BDG tests undertaken from February 2020 through to December 2020 on 66 post lung transplant recipients with suspected or confirmed fungal infection. Tests were ordered following multidisciplinary team discussions with transplant physicians and clinical microbiologists. <h3>Results</h3> Of 115 tests, 50 were positive of which 12 contributed to the early diagnosis of a fungal infection, 36 were used to follow response to treatment in a confirmed fungal infection and 2 were falsely positive. Infections diagnosed were invasive aspergillosis (8), invasive candidiasis (1), Pneumocystis jirovecii pneumonia (1), cryptococcal meningitis (1) and invasive Scedosporium apiospermun infection (1). Of the 65 negative tests, 43 contributed to an invasive fungal infection being ruled out and empiric antifungal therapy being discontinued or avoided without any adverse consequences. 5 negative tests did not result in de-escalation from antifungal therapy. 17 tests were repeat tests undertaken as follow-up. <h3>Conclusion</h3> In our cohort, the turbidimetric BDG had a sensitivity and specificity of 100% and 97% respectively, with a positive predictive value of 96% and negative predictive value of 100%. The high efficiency of this test is likely influenced by the diagnostic stewardship applied in ordering the test, raising the pre-test probability. Turn-around times were 1 day average with a range of 1-7 days. The high negative predictive value allowed negative BDG results to be used as an antimicrobial stewardship tool. A direct saving of €9,053 was made as a result of empiric antifungal therapy being stopped following a negative BDG result. In conclusion, the turbidimetric assay for BDG is efficacious for confirming or ruling out fungal infection in post-lung transplant patients.