Not all peritoneal membranes are created equally. The peritoneal equilibration test (PET) is a standardized method for assessing peritoneal membrane function, and is used for tailoring an appropriate, individualized PD prescription.
The test is based on the fact that different peritoneal membranes have different transport characteristics. For "high transporters", solute exchange occurs rapidly, but as a result the osmotic gradient provided by the PD solution dextrose dissipates rapidly and sometimes these patients run into problem with ultrafiltration. They are best managed with shorter, frequent exchanged and may be excellent candidates for a cycler. In contrast, "low transporters" exhibit inefficient solute exchange and may require prolonged dwell times. The majority of patients fortunately fall in the "intermediate transporter" range and can usually be managed with either CAPD or CCPD strategies, whichever is more convenient.
The PET test involves beginning a PD dwell and then taking blood and dialysate samples at different time points. The D/P ratio (dialysate-to-plasma) of creatinine, BUN, and glucose is measured. Patients with a high D/P ratio (e.g., >0.8 at 4 hours) are considered high transporters whereas those with a low D/P ratio (e.g., <0.5 at 4 hours) are considered low transporters.