False positive galactomannan results in adult hematological patients treated with piperacillin-tazobactam

In this prospective study including 78 adult patients with haematological malignancy (90 episodes) we performed galactomannan (GM) (Platelia Aspergillus) screening twice weekly for the diagnosis of invasive aspergillosis. There were five proven and four probable invasive aspergillosis cases. The sensitivity, specificity and positive and negative predictive values were 100, 88, 47 and 100%, respectively. There were eight patients with false positive GM (10.2%). In six patients the false GM reactivity was due to the administration of piperacillin-tazobactam (P-T). A significant association was found between false positive GM (= or > 0.5) and the administration of P-T (p < 0.01). Two other patients with no invasive aspergillosis (2.5%) and false GM reactivity had graft versus host disease (GVHD) and one of them had also mucositis grade IV. The kinetic patterns of false positive GM due to P-T is discussed.