Aspergillus PCR testing: results from a prospective PCR study within the AmBiLoad trial

Objectives: Invasive fungal infection (IFI) is a major cause of morbidity and mortality in severely immunocompromised patients and is difficult to diagnose. The significance of molecular methods for diagnosis of IFI is still controversial. In a subset of patients treated within the AmBiLoad Trial, samples were investigated prospectively by a nested Aspergillus PCR assay to re‐evaluate the significance of PCR in this setting. Patients and methods: In the randomized, prospective multicenter AmBiLoad trial, patients with proven or probable IFI were randomized to receive liposomal amphotericin B (L‐AMB) 3 or 10 mg/kg QD for 14 d followed by L‐AMB 3 mg/kg QD. From 91 patients, 459 serial samples (98% blood samples) were investigated by a nested PCR assay for Aspergillus DNA. All samples were investigated in our laboratory with a previously described nested and a quantitative PCR assay. As required by the study protocol, serial Aspergillus antigen galactomannan was performed. IFI was defined according to modified EORTC/MSG 2002 criteria as applied in the AmBiLoad trial. Results: Seven and 52 patients had proven and probable IFI according to modified EORTC/MSG criteria, respectively. The median number of samples investigated per patient was 4. Seventy percent of samples were obtained during treatment with antifungal study medication. Forty‐three samples gave positive PCR results. Patients with an unfavorable outcome had a significantly higher rate of positive PCR results (48% versus 21%). Conclusions: The sensitivity of Aspergillus PCR testing is limited during antifungal therapy. The tendency for persistently positive PCR results to indicate a poor prognosis has to be confirmed in further studies.