Diagnosis of invasive aspergillosis in bone marrow transplant recipients by polymerase chain reaction

A nested polymerase chain reaction (PCR) test targeting Aspergillus spp, la rge ribosomal subunit genes was evaluated retrospectively on 175 serum samp les from 37 bone marrow transplant recipients, 70% of whom received grafts from unrelated donors. Six patients had proven infection, seven had probabl e infection, and three had possible infection, using the revised EORTC case definitions. These 16 patients were all PCR positive (57 out of 93 samples tested). Two additional patients who did not fulfil current diagnostic cri teria, but in whom invasive aspergillosis (IA) was thought clinically proba ble, were also PCR positive (five out of nine samples). Invasive aspergillo sis was unlikely in the remaining 19 patients, four of whom were PCR positi ve on a single occasion (four out of 70 samples). Three samples were inhibi tory to PCR. Sensitivity of PCR in diagnosing patients with IA was 100%, sp ecificity was 79% and positive predictive value was 80%, using the criterio n of a single positive result. If two positive results were required, these values were 81%, 100% and 100% respectively. The median duration of infect ion documented by PCR was 36 days (range 3-248 days) in 17 out of 18 patien ts (94%) who did not survive. Positive PCR results predated the institution of antifungal therapy in two-thirds of patients. Four patients became PCR positive during pretransplant conditioning therapy.