Recovery from neutropenia can be predicted by the immature reticulocyte fraction several days before neutrophil recovery in autologous stem cell transplant recipients

The duration of neutropenia (absolute neutrophil count (ANC) ≤100/ μl) identifies cancer patients at risk for infection. A test that precedes ANC ≥ 100/μl would be of clinical value. The immature reticulocyte fraction (IRF) reflects erythroid engraftment and hence a recovering marrow. We evaluated the IRF as predictor of marrow recovery among 90 myeloma patients undergoing their first and second (75 patients) melphalan-based autologous stem cell transplantation (Mel-ASCT). The time to IRF doubling (IRF-D) preceded ANC ≥ 100/μl in 99% of patients after the first Mel-ASCT by (mean ± s.d.) 4.23 ± 1.96 days and in 97% of the patients after the second Mel-ASCT by 4.11 ± 1.95 days. We validated these findings in a group of 117 myeloma patients and 99 patients with various disorders undergoing ASCT with different conditioning regimens. We also compared the time to hypophosphatemia and to absolute monocyte count ≥100/μl to the time to ANC ≥ 100/μl. These markers were reached prior to this ANC end point in 55 and 25% of patients but were almost always preceded by IRF-D. We conclude that the IRF-D is a simple, inexpensive and widely available test that can predict marrow recovery several days before ANC ≥ 100/μl.