[Is body surface area (BSA) suitable for indexing renal and dialysis clearances and other physiological parameters? A theoretical approach and a critical analysis (part 3)]

Many parameters of biological functions, interesting different branches of medicine, have to be indexed by the same value for each other comparison between single individuals or between-within groups. Body Surface Area (BSA) and 1.73 m2 reference value are probably the most used tools for indexation, but a growing number of scientific papers emphasize the risk of under or over estimates of data by BSA indexation in overweight--obese or on the contrary underweight individuals. This study has been planned to evaluate this problem a) by a theoretical approach, indexing to 1.73 m2 the creatinine clearance (CtCl) in an ideal population and b) analysing and debating the doubts and problems about the indexation by BSA in many fields, the possibilities of indexation by other methods, or to use BSA with different approach, to reduce the risk of bias, evaluating the possibility of this target in a real population of 45 men and 84 women undergoing Peritoneal Dialysis (PD)--III--There is a lack of significative correlation between BSA and GFR, this one on the contrary significantly correlated with lean body mass and body water, possible alternatives to BSA. Researches performed to validate the indirect estimates of above variables by creatinine excretion and bioimpedance don't seem up till now to give sufficient evidences for a general acceptance. In conclusion, it would be advisable or to drop the indexing by BSA or, if necessary, to use it by different methods, as theoretically shown in this paper.