Fungal infections are among the most serious complications in neutropenic patients. A major problem that has compromised management of fungal infections is healthcare professionals' inability to recognize the infections when they occur. No adequate diagnostic tools exist to detect many of the fungal infections. Early diagnosis of disseminated candidiasis is a challenge because only 35%-50% of neutropenic patients have positive blood cultures (Bodey, 1997), and radiologic tests have low specificity in that patient population. For example, a routine chest x-ray can be negative, yet a computed tomography (CT) scan of the chest can be positive for pneumonia the next day. Therefore, fungal infections often are advanced before diagnostic confirmation; thus, overall outcomes are poor. A great effort has been invested in developing serologic tests to detect circulating antigens of fungi.