Assessment of PD treatment delivered by 125I-Iothalamate plasma disappearance.

The calculation of treatment delivered to PD patients requires the collection of PD effluent, plasma and urine samples. 125 I-Iothalamate plasma disappearance, which eliminates the need for PD effluent collections, was tested as an alternate method to measure the weekly PD treatment delivered. Two protocols were designed. In protocol A, a 35 μCi dose of 125 I-Iothalamate was injected in three subjects and allowed to equilibrate. A plasma sample was taken and patients returned on both of the following two days with timed labeled effluent bags and a 24-hour urine collection for each day. The timed PD effluent and 24-hour urine collections were measured for 125 I-Iothalamate, urea and creatinine concentrations. 125 I-Iothalamate and urea clearances were strongly correlated for both PD (R 2 = 0.76, n = 24) and renal (R 2 = 0.92, n = 6) clearances. In protocol B, thirteen subjects were given a 35 μCi injection of 125 I-Iothalamate. A blood sample was taken one hour post injection and a second blood sample taken on day five. Kt/V were calculated from the 125 I-Iothalamate plasma disappearance curve and compared to weekly Kt/V values extrapolated from one day's collections (Traditional Method). The comparison of Kt/V values found by 125 I-Iothalamate Method vs. the Traditional Method yielded R 2 = 0.79, n = 13. In conclusion, the plasma disappearance of 125 I-Iothalamate is an alternate method of determining weekly Kt/V, over an extended period of time, which eliminates the need for PD effluent collections.