Peritoneal equilibration test (PET)
The PET is a standardized procedure for assessing the permeability and efficiency of a patient’s membrane to exchange small solutes and fluid.
The PET uses a series of dialysate (D) and plasma (P) samples obtained over a 4-hour period to measure solute equilibration (D/P creatinine), rate of glucose absorption, and net fluid removal or “ultrafiltration”.
After determining these values, the patient’s peritoneal membrane is categorized into one of the four membrane transport classifications.
Each membrane classification (slow, slow average, fast average, fast) has specific characteristics that guide the clinician in tailoring the patient’s dialysis prescription. An example of results from a typical standard PET is included. In general, patients found to have fast to fast average membrane transport characteristics should be prescribed shorter dialysis dwell times to enhance fluid and small solute removal. Rapid equilibration of waste between dialysate and plasma, along with absorption of the osmotic agent (dextrose) by abundant peritoneal capillaries, are the reason for this.
The standard PET is usually done with a 2.5% (2.27% anhydrous) dextrose PD solution, but a 4.25% (3.86% anhydrous) dextrose solution can be used as an alternative. The benefit of using the latter is that it produces near-identical diffusive results to a 2.5% solution and provides additional information about maximal UF capacity of the peritoneal membrane being tested. Reproducible and accurate results have been demonstrated with either solution.