Detection of candidaemia in patients with and without underlying haematological disease

Abstract number: P901

Arendrup M.C., Bergmann O.J., Larsson L., Nielsen H.V., Jarløv J.O., Christensson B.

Objectives: The diagnosis of candidaemia remains difficult despite the development of new diagnostic tools. We here compare the diagnostic potential of three different blood culture systems, D/L arabinitol, antigen, and antibody detection.

Methods: 114 episodes in 93 patients with either underlying haematological disease and fever without response to antibacterial treatment or documented systemic Candida infection were enrolled prospectively. A pro forma was provided to gather clinical and para-clinical information on all patients. Blood culture (BC) was done using a conventional blood culture (2 aerobic and 2 anaerobic bottles), a fungal blood culture (Mycosis bottle, BACTEC), and the Isolator 10 lysis centrifugation blood sample (Isolator 10, Wampole). Surveillance cultures from oropharynx, urine, and faeces were performed. The D/L arabinitol ratio in serum and urine was determined by gas chromatography (Larsson L, 1994). Antigen (Ag) was detected by the CandTec Kit (Ramco Laboratories Inc., Vernn, Houston, USA) and by using the Platelia Candida Ag ELISA kit (Bio-Rad, France) and anti-Mannan antibody (Ab) was detected using Platelia Candida AB/AC/AK kit (Bio-Rad, France).

Results: The 114 episodes were classified as proven invasive candidiasis (24), probable (14), possible (52), or unlikely (24). Candidaemia involved C. albicans (17 episodes), C. albicans + C. glabrata (3 episodes), C. tropicalis (1 episode), and yeast not identified (1 episode). The mycosis bottle was the only BC positive in 2 episodes and the conventional blood culture the only BC positive in 1 episode. Evaluating only the proven and unlikely episodes sensitivity (sens) and specificity (spec) of the indirect tests were as follows Mannan Ag & anti-Mannan Ab: 83.3%, 78.3%; D/L arabinitol ratio in serum: 41.7%, 86.4%; CandTec Candida Ag: 66.6%, 70.8%. By lowering the cut off values to Mannan Ag: 0.10 ng/ml and anti-Mannan Ab: 4 AU/ml the values were: sens 100%, spec 73.9%, PPV 80% and NPV 100%, and by applying the D/L arabinitol ratio to only patients with haematological neutropenia the values were: sens 75%, spec 90.5%, PPV 60%, and NPV 95%.

Conclusion: The fungal blood culture bottle slightly improved the detection of candidaemia. Among the indirect tests the combined use of Mannan Ag and anti-Mannan Ab showed the best performance especially when cut offs were lowered. D/L arabinitol ratio seemed useful in the setting of haematological underlying disease and neutropenia.