Assessment of the lightcycler PCR assay for diagnosis of invasive aspergillosis in paediatric patients with onco-haematological diseases.

A reliable diagnosis of invasive aspergillosis (IA) is hampered by the difficulty in obtaining suitable tissue samples. To evaluate the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the LightCycler PCR for the diagnosis of IA, 536 blood samples were collected over a 22-month period from 62 paediatric patients (median age 10 years, range 1-18) considered at risk of IA. The galactomannan antigen (GM) and fungal DNA were assessed on serial blood samples. IA was diagnosed in eight of 62 patients (13%): proven, five, probable, three. Sensitivity, specificity, PPV and NPV of LightCycler PCR varied according to the number of positive samples used to define positivity: 88%; 37%; 17% and 95% for single sample positivity; and 63%, 81%, 33% and 94% for serial sample positivity respectively. The concordance between positivity of LightCycler PCR assay and the diagnosis of IA was 79%. The single positivity of LightCycler PCR assay showed a good sensitivity for the diagnosis of IA in paediatric patients. The high NPV makes LightCycler PCR a promising tool in addition to GM testing to design a strategy of pre-emptive antifungal therapy, although further validation studies are needed.