The peritoneal equilibration test (PET) is a semiquantitative assessment of peritoneal membrane transport function in patients on peritoneal dialysis [1,2]. The solute transport rates are assessed by the rates of their equilibration between the peritoneal capillary blood and dialysate. The ratio of solute concentrations in dialysate and plasma (D/P ratio) at specific times (t) during the dwell signifies the extent of solute equilibration. This ratio can be determined for any solute that is transported from the capillary blood to the dialysate. Creatinine, urea, electrolytes, phosphate, and proteins are the commonly tested solutes for clinical use.
Since glucose is absorbed from the dialysate to blood and very quickly metabolized, a conventional D/P ratio for glucose is meaningless. Instead, the fraction of glucose absorbed from the dialysate at specific times can be determined by the ratio of dialysate glucose concentrations at specific times (t) to the initial level in the dialysis solution (Dt/D0). The PET also helps measure ultrafiltration and residual volumes [3,4].
An overview of the peritoneal equilibration test is presented here. A detailed analysis of the utility of this examination in evaluating patients with less than adequate clearances or ultrafiltration is presented separately. (See "Problems with solute clearance and ultrafiltration in continuous peritoneal dialysis".)
ELEMENTS OF THE PERITONEAL EQUILIBRATION TEST
The PET is a highly reproducible procedure consisting of a standardized four-hour dialysis exchange with a dialysis solution . The test permits the comparison of multiple results in a patient over a long period of therapy; in addition, the results between patients within a center and between populations from different geographic locations may be compared.
The PET is standardized for the following elements :