Patients with pulmonary and cardiac disease show an elevated proportion of immature reticulocytes.

The value of reticulocyte analysis has been largely confined to classification of anaemia. In the present study, we have investigated the value of undertaking automated fluorescent reticulocyte analysis (Abbott Cell-Dyn 4000) in patients with pulmonary or cardiac diseases. A control group of nonanaemic (n = 367) and anaemic patients (n = 57) was established and thereafter compared with a group of patients with pulmonary disease (172 without anaemia, 92 with anaemia) and another group with cardiac disease (520 without anaemia, 254 with anaemia). The Hb level and reticulocyte RNA content (as measured by the immature reticulocyte fraction, IRF) of the study subjects were inversely correlated (r = -0.41). The mean IRF of nonanaemic patients with pulmonary (mean = 0.331, SD=0.124) and cardiac disease (mean = 0.266, SD = 0.079) were both significantly higher (P < 0.05) than in control subjects (mean = 0.220, SD = 0.062). Nonanaemic and anaemic patients with cardiac disease both showed significantly higher (P < 0.05) reticulocyte percentage counts than the equivalent anaemic and nonanaemic controls. Each of these phenomena can all be attributed to hypoxia mediated EPO production. Our observation that 35% of patients with pulmonary disease have elevated levels of IRF, may prove useful in screening for tissue hypoxia in nonanaemic patients. Furthermore, serial monitoring of the IRF may prove valuable in observing the efficacy of therapy in these patients.