A clinical parameter that evaluated the dynamics of neutropenia, combining intensity and duration, could be a good tool to identify patients at high risk for IMI. This tool could be used to stratify patients, helping clinicians to select appropriate candidates for early antifungal therapy (empiric or preemptive) in persistently febrile neutropenic patients. We developed an index (called D-index) that uses data from white blood cell counts (WBC), and combines intensity and duration of neutropenia. This index was tested in patients with acute myeloid leukemia, and showed a good discriminatory performance in identifying patients with IMI and without IMI. A cutoff was derived, and showed good sensitivity, specificity and a very high negative predictive value (97 to 99%) [7]. The high negative predictive value of this index is very similar to that obtained with GM and 1,3-beta-D-glucan in febrile neutropenic patients [8,9]. With this regard, the D-index could be of help to assess the pre-test probability of IMI and help to interpret the results of positive serum GM and / or 1,3-beta-D-glucan: patients with low values of D-index would be best interpreted as having false-positive results of these tests. Similarly, positive biomarkers in the presence of a high D-index would be more likely to be true positives, since the combination of different tests may increase their positive predictive value.