False-positive results of the turbidimetric β-D-glucan assay in patients with bacteremia.

BACKGROUND

The presence of bacteremia is described as a cause of false-positive (FP) elevation of serum (1→3)-β-D-glucan (BDG) levels measured with the Fungitell colorimetric assay. The experience with the increasingly used turbidimetric Wako BDG assay in this scenario is limited.

METHODS

We recruited 58 patients with proven bacteremia and no clinical suspicion of invasive fungal disease between October 2022 and July 2023. Serum BDG was assessed by the Wako test in blood samples collected immediately upon the confirmation of blood culture positivity (median interval of 3 days (interquartile range [IQR]: 2 - 5)). The positivity threshold was set at 7 pg/mL as per manufacturer's instructions.

RESULTS

The most common sources of bacteremia were urinary tract infection (27.6%) and intraabdominal or hepatobiliary infection (24.1%). Predominant pathogens included Staphylococcus aureus (44.1%), Escherichia coli (22.0%) and Klebsiella pneumoniae (15.5%). Most of the patients (91.4%) received a β-lactam-containing regimen. A positive BDG assay was obtained in 5 patients, yielding a FP rate of 8.6% (95% confidence interval: 2.9 - 18.9). The median BDG was 8.6 pg/mL (IQR: 7-9 - 12.4). All but one patient had at least one alternative cause of FP results in the BDG assay, including hemodialysis, colitis, albumin therapy and gauze exposure. One patient with persistently elevated BDG levels was eventually diagnosed with Candida esophagitis.

CONCLUSIONS

The occurrence of FP results with the turbidimetric BDG assay is uncommon, involves moderate reactivity and is typically accompanied by other potential causes of serum BDG elevation.