The Accuracy of 1,3-B-D-glucan testing in diagnosing Fungal Infections: A comparison of high-risk groups within the ICU setting

1,3-B-D-Glucan [BDG] is found in the cell wall of most fungii species and BDG testing is currently used as an adjunct for diagnosing fungal infections in immunocompromised patients. Guidelines on use of BDG testing is still unclear due to uncertainties on its reliability as a diagnostic tool. We aimed to determine the accuracy of BDG testing for diagnosing fungal infections and observed general patient demographics for those more at-risk of infection within the ICU setting. A case control study was carried out on 158 patients who had BDG tests requested in UH Bristol. This was further divided into 69 positive BDG result group and 89 negative BDG result control. Patient BDG results were compared to gold standard diagnostic criteria of positive signs on CT scans, BAL PCR and Blood or sputum cultures to confirm presence of fungal infection. Control group implied negative BDG test results consistent with negative gold standard diagnostic testing results in order to determine true negative cases. We determined BDG to have Sensitivity of 89.2%, Specificity of 66.9%, Positive predictive value of 36.3% and Negative Predictive value of 97.8%. Majority of ICU patients affected by fungal infections requiring BDG testing included stem cell transplant, neutropenic, GI surgical and Haematology admissions. In conclusion, BDG has a large Negative Predictive Value and is a good test to use in excluding fungal infections. However, it has limited sensitivity and positive BDG is not helpful in confirming presence of fungal infections.