Relationship between red blood cell distribution width and kidney function tests in a large cohort of unselected outpatients.

Objective: A strong, independent, association has recently been shown between higher red blood cell distribution width (RDW) and the risk of all-cause death and cardiovascular events. However, the mechanism(s) underlying this association remains unclear. Since impaired kidney function is a well-known risk factor for cardiovascular disease, we assessed whether RDW is associated with decreased kidney function.

Material And Methods: We cross-sectionally assessed results of RDW, haemoglobin, main corpuscular volume (MCV) and serum creatinine levels in a large cohort of unselected adult outpatients consecutively referred by general practitioners for routine medical check-up. Glomerular filtration rate (GFR) was estimated using the abbreviated Modification of Diet in Renal Disease (MDRD) equation.

Results: Cumulative results of RDW, creatinine and other variables were retrieved from the database of our Laboratory Information System for 8,585 adult outpatients over a 3-year period. When participants were grouped according to RDW quartiles, there was a strong, graded, decrease in estimated GFR levels (ranging from 87+/-18 to 81+/-32 mL/min/1.73 m(2); p<0.0001). Accordingly, the percentage of participants with estimated GFR<60 mL/min/1.73 m(2) increased steadily across RDW quartiles (from 5 % to 19 %; p<0.0001). In logistic regression analysis, lower estimated GFR strongly predicted higher RDW levels (p<0.0001) independently of age, gender, MCV and haemoglobin values.

Conclusions: Our findings suggest that there is an inverse, graded, association between RDW and kidney function tests in a large cohort of unselected adult outpatients.