Association of Red Blood Cell Distribution Width (RDW) with Laboratory Parameters in Anemic Adults.

Abstract 5083

RDW, a quantitative measure of anisocytosis, has been utilized for many years in the differential diagnosis of anemia. More recently, studies have reported that RDW varies with renal function and markers of inflammation, and that RDW is a predictor of mortality (Scand. J. Clin. Lab. Invest. 2009; 68:745-8; Arch. Pathol. Lab. Med. 2009; 133:628-32; Arch. Intern. Med. 2009; 169:588-94). However, these reports were based on studies of large populations of unselected outpatients, many of whom were hematologically normal. Utilizing a de-identified database of 32 anemic adult inpatients (17 male/15 female, 27 Caucasian) who had undergone diagnostic bone marrow examination as part of an earlier study (J. Clin. Lab. Haematol. 1999; 21:161-7), associations between RDW and clinical laboratory parameters in a more restricted patient subset were examined.

RDW values for 26/32 patients were in the highest quintile observed in the National Health and Nutrition Examination Survey (RDW > 13.8%). Significant differences between patients in the highest quintile and other patients were observed for hemoglobin concentration (9.9 g/dL vs. 11.6 g/dL, p = 0.01), serum soluble transferrin receptor (sTfR) (30.3 nM vs. 16.7 nM, p = 0.02), and serum interleukin (IL)-1 (1.6 pg/mL vs. 0.3 pg/mL, p =0.03). No other significant differences were observed in other automated hematologic markers, in biochemical indicators of iron status, renal function, or inflammation, or in marrow aspirate iron score. When the correlation between RDW and the other parameters studied was evaluated, the only statistically significant correlations found were with C-reactive protein (CRP) (r = -0.49, p = 0.009) and sTfR (r = 0.53, p = 0.002). The significance of the correlation between sTfR and RDW was independent of other indicators of iron status, CRP, and serum IL-1. In contrast, the significance of the correlation between CRP and RDW was dependent on variation in sTfR and serum ferritin concentrations. In this group of patients with who generally had either high-normal or high RDW values, CRP and RDW were inversely correlated.

In summary, associations between RDW and other laboratory or clinical parameters observed in unselected patient populations may not be applicable to complex anemic inpatients. The association between sTfR concentration and RDW appears to be independent of the relationship between sTfR concentration and patient iron status.