Relationship between hematocrit and renal function in men and women

Background. Anemia is a known complication of renal insufficiency, but the relationship between level of renal function and magnitude of reduction in hematocrit is not well defined. Men have higher hematocrit and absolute glo merular filtration rate (GFR) than women: however, it is unknown whether th e level of clearance associated with decreased hematocrit is the same in me n and women. Methods. We conducted a cross-sectional study of 12,055 adult ambulatory pa tients. General linear models were used to analyze the relationship between hematocrit and Cockcroft-Gault equation estimated creatinine clearance (C- Cr: mL/min) and Modification of Diet in Renal Disease (MDRD) formula estima ted the GFR indexed to body surface area (mL/min/ 1.73 m(2)). Results. The hematocrit decreased progressively below estimated C-Cr 60 mL/ min in men and 40 mL/min in women. Com pared with subjects with C-Cr >80 mL /min, men with C-Cr 60 to 50 mL/min, 50 to 40 mL/min, 40 to 30 mL/min, 30 t o 20 mL/min, and less than or equal to 20 mL/min had mean hematocrits that were lower by 1.0, 2.4, 3.7, 3.5, and 10.0%, respectively; the correspondin g reductions in women with C-Cr, 40 to 30 mL/min, 30 to 20 mL/min, and (20 mL/min were 1.7, 2.9, and 6.3% tall P < 0.05). This between-sex difference diminished when renal function measurement was indexed to body size. Compar ed with subjects with GFR >80 mL/min/1.73 m(2), men with GFR 50 to 40 mL/mi n/ 1.73 m(2), 40 to 30 mL/min/1.73 m(2). 30 to 20 mL/min/1.73 m(2), and les s than or equal to 20 mL/min/1.73 m(2) had mean hematocrits that were lower by 2.0, 4.4. 5.3, and 9.4%: the corresponding reductions in women with GFR 50 to 30 mL/min/1.73 m(2), 40 to 30 mL/min/ 1.73 m(2), 30 to 20 mL/min/1.7 3 m(2) and less than or equal to 20 mL/min/1.73 m(2) were 0.6, 1.6, 3.8, an d 5.3% (all P < 0.05). Conclusions. A decrease in hematocrit is apparent even among patients with mild to moderate renal insufficiency. At any given level of renal function below estimated C-Cr 60 mL/min, men have a larger decrease in hematocrit th an women.