Diagnosis of invasive fungal infections by RQ-PCR assay in pediatric acute leukemia induction.

Abstract

9579 Background: Sensitive and specific diagnostic tools for invasive fungal infections (IFI) in acute leukemia (AL) patients are lacking. Blood cultures are often negative and performing invasive procedure is difficult in critically ill patients. Studies on fungal DNA detection by RQ- PCR in childhood leukemia induction are lacking. Pan-AC PCR assay used in present study targets 28S subunit of fungal rDNA and detects 10 Candida and 6 Aspergillus species Methods: Out of 100 randomized pediatric AL patients receiving antifungal prophylaxis with voriconazole/ amphotericin B, single peripheral whole blood sample in EDTA was used for RQ-PCR assay in patients who failed prophylaxis due to proven, probable, possible or suspected fungal infections (FI). PCR results were retrospectively correlated with clinical profile Results: Single reaction RQ-PCR test was positive in 18/29 (62%) patients who failed prophylaxis. In the only patient with proven FI (mucormycosis), RQ-PCR assay was negative. No patient had probable FI. RQ-PCR was positive in 2/4 (50%) patients with possible and 16/24 (66.6%) suspected FI and 4/10 (40%) patients with pneumonia. By applying method A/B (Maertens et al, Blood 2001), sensitivity and positive predictive value (PPV) could not be commented due to no proven Aspergillus or Candida infections; specificity and negative predictive values (NPV) were 41% and 100% respectively; by method C (included episodes of possible IFI as true positive), sensitivity, specificity, PPV and NPV were 50%, 36%, 11% and 81% respectively. Two patients died on PCR positive arm as compared to none in PCR negative arm (p=0.218). Total number therapeutic antifungal days were similar in PCR-positive and PCR-negative group (p=0.475). In suspected FI patients, 8/24 (33.3%) were PCR negative and unnecessarily received empirical antifungal therapy (EAFT). Conclusions: RQ-PCR is a practical, rapid, non-invasive screening test for excluding IFI in pediatric AL. The high NPV makes RQ-PCR a promising tool to use this prior to initiating EAFT in antibiotic resistant febrile neutropenic pediatric AL patients; this would avoid toxicity, cost and hospitalization for EAFT (ClinicalTrials.gov identifier:NCT00624143). No significant financial relationships to disclose.