Can bacteraemia lead to false positive results in 1,3-beta-D-glucan test? Analysis of 83 bacteraemia episodes in high-risk patients for invasive fungal infections.

BACKGROUND: Although bacteraemia has been reported to be related to false positive results in the 1,3-beta-D-glucan (BDG) test, the evidence for this interaction is limited. AIMS: To investigate the association between bacteraemia and the BDG test. METHODS: Records of the Infection Control Committee were reviewed to identify bacteraemia in patients who were hospitalized in the haematology ward and stem cell transplantation unit. Patients who had undergone the BDG test at least once within 5 days of a positive blood culture were included in the study. BDG levels in the sera were assayed using the Fungitell kit (Associates of Cape Cod, East Falmouth, MA) according to the manufacturer's specifications. The cutoff for BDG positivity was 80 pg/mL. RESULTS: Eighty-three bacteraemic episodes were identified in 71 patients. BDG positivity was detected in 14 patients with bacteraemia, and only 1 patient with Escherichia coli bacteraemia had high BDG levels (over 80 pg/mL) despite having no evidence of invasive fungal infection (IFI). CONCLUSIONS: Our study suggests that the cross-reactivity of the BDG test with a concomitant or recent bacteraemia is a very rare condition. Patients with risk factors for IFI should be evaluated cautiously when a positive BDG test is reported.

Does ampicillin-sulbactam cause false positivity of (1,3)-beta-D-glucan assay? A prospective evaluation of 15 patients without invasive fungal infections.

The purpose of this study was to investigate the interaction between intravenous ampicillin-sulbactam treatment and (1,3)-beta-D-glucan (BDG) assay. Fifteen patients with a median age of 60 (16-81) without known risk factors for invasive fungal infections who received a daily dose of 3×2g ampicillin-sulbactam monotherapy from different batches were included in the study. Thirteen patients had soft tissue infections. The 5 of 13 patients who went under surgery had surgical dressings. Serum samples were obtained both before and after antibiotic infusion on the first, third, seventh and tenth days of an ampicillin-sulbactam treatment course. BDG was assayed using the Fungitell kit (Associates of Cape Cod, East Falmouth, MA, USA) according to manufacturers' specifications. All serum samples were also tested for galactomannan (GM) antigenemia by Platelia Aspergillus ELISA (Bio-Rad Laboratories, Marnes-la-Coquette, France). A total of 37 of 117 serum samples were positive for BDG at a threshold of 80pg ml(-1) . Seven of 37 BDG positive serum samples had a GM index ≥0.5. When a cutoff value of ≥0.5 was used for GM positivity, 16 (13.3%) serum samples were positive. For a cutoff value of ≥0.7, eight (6.6%) serum samples were positive. There were no statistically significant differences in the median BDG levels (P=0.47) or median GM indices (P =0.28) of the various sampling times. None of the SAM vials tested positive for BDG or GM. After ruling out fungal infections and all known potential causes of false BDG positivity, environmental contamination remained possible cause of BDG reactivity. We did not observe any significant association of ampicillin-sulbactam administration and positive assays for BDG or GM.