Impossibility of Comparing Data of Indexed Peritoneal Creatinine Clearance when Different Formulae of Body Surface Area are Used
Background This study aimed to determine the differences arising form indexing a measured physiological variable by using different body surface area (BSA) estimation formulae. Methods The studied variables were the overall measured peritoneal creatinine clearance plus residual renal clearances (MeasCtCl) of 19 men and 23 women in a stable condition who were undergoing peritoneal dialysis and were a mean 55.7 ± 15.8 and 55.1 ± 14.1 years of age, respectively. The patients had comparable body mass indexes (BMIs; 25.01 ± 4.14 in men and 24.5 ± 3.46 in women). The MeasCtCls were indexed to 1.73 m2 using 5 formulae: by Du Bois, Boyd, Mosteller, Livingston and Yu. The numerical and percentage differences between the MeasCtCl values and each approach to indexation were calculated, as well as the differences between the indexations. Paired t-test and similarity percentage test were used to evaluate the significance of the differences. Results The impossibility of adequately comparing data indexed according to different BSA estimation formulae was shown, documenting a high risk of erroneous evaluations and conclusions. Conclusions Some methods to avoid these errors in clinical applications are suggested, as well as the possibility of indexing only to height.