Protein Loss in Peritoneal Effluent: Different Meaning for 24-h versus PET Samples

Quantification of peritoneal protein loss (PPL) may be expressed according to a timely collection (24-h measurement or 4-h PET assessment) and as a concentration. The aim of this study was to compare the quantification methods of 24-h and 4-h collections.This study included 81 prevalent peritoneal dialysis patients. Demographics and clinical and bioelectrical impedance features were registered. PPL was measured (4-h PET and 24-h results) and peritoneal protein clearance was calculated. A linear regression model was performed.Age and continuous ambulatory peritoneal dialysis (compared to cycler) were positively associated with greater PPL on 24-h collections. Neither cardiovascular disease, hypertension, diabetes nor the comorbidity Charlson Index was significantly associated with PPL. There was a consistent univariable relationship with D/P creatinine, whichever sampling method was used. Only 24-h measurements of PPL correlated with body composition variables. In multiple linear regression analysis, D/P creatinine association with PPL stands out. On the other hand, 24-h determinations (in grams or clearance) were associated with overhydration. PET protein quantification was associated with peritoneal creatinine clearance.Different methods sign different pathophysiological pathways. PET protein loss quantification should be regarded as a marker of peritoneal membrane intrinsic permeability. Measurements of a 24-h sample might be closer to patients' clinical status and prognosis, signalizing opportunities for therapy intervention.