Gender differences in normalized clearances in CAPD: role of body size and normalizing parameters

Area of Science:

• Nephrology
• Renal Physiology
• Dialysis

Background:

• Continuous ambulatory peritoneal dialysis (CAPD) is a common renal replacement therapy.
• Assessing dialysis adequacy involves measuring solute clearances, such as urea and creatinine.
• Normalization of clearances is often performed to account for body size differences between individuals.

Purpose of the Study:

• To compare raw and normalized urea and creatinine clearances between men and women undergoing CAPD.
• To investigate whether observed gender differences in clearances are artifacts of the normalization process.

Main Methods:

• Retrospective analysis of clearance studies from 302 CAPD patients (135 women, 167 men) across four academic medical centers.
• Urea and creatinine clearances were measured using standard methods.
• Urea clearance was normalized by the volume of distribution (V), and creatinine clearance was normalized by V and body surface area (BSA).

Main Results:

• Men exhibited higher raw total urea and creatinine clearances compared to women.
• Normalization by V resulted in higher urea clearance (Kt/Vur) in women, while normalization by BSA resulted in higher creatinine clearance (Ccr) in men.
• Significant differences (p < 0.001) were observed, with men having larger V and BSA, but women having a higher body mass index.

Conclusions:

• Normalization of dialysis clearances can introduce artificial gender-specific differences.
• Normalization by body water (V) favors women, while normalization by body surface area (BSA) favors men.
• Clinicians should be aware of these normalization-induced differences when interpreting clearance data between genders.