Prediction of renal transplant survival from early postoperative radioisotope studies

it has been routine at the University of Alabama Medical Center to obtain a radionuclide renal function study immediately after transplantation (usual ly within 3 d) that includes estimation of effective renal plasma flow (ERP F) from a single plasma sample in addition to imaging. We present here the correlation between baseline measurements and the 1-y graft survival. Metho ds: Two cohort years were reviewed: 1988, when I-131-orthoiodohippurate (OI H) was used; and 1995, when Tc-99m-mercaptoacetyltriglycine (MAG3) was used . ERPF was measured concurrently with gamma-camera imaging by previously pu blished single-injection, single-sample methods (converting MAG3 clearance to ERPF by means of a correction factor). Results: Graft survival during th e first postoperative year improved significantly in the interval between c ohort years, from 74% of 147 cadaver (GD) grafts in 1988 to 91% of 200 GD g rafts in 1995 (log rank test, P < 0.05). In contrast, for living related do nor (LRD) grafts there was no significant change, from 91% of 66 in 1988 to 91% of 83 in 1995. The baseline ERPF was a significant predictor of graft survival in both 1988 and 1995 (Wilcoxon test, P > 0.05). For LRD grafts th e association was not significant in either year. Using MAG3 (1995), the pe ak time and the ratio of counting rate (R) at 20 min to that at 3 min (R20: 3) were also significant predictors for GD graft survival. Using OIH (1988 cohort), the correlation with peak time did not reach significance, and the R20:3 measurement was not available. Although multivariate combinations (C ox proportional hazards model) did not have significantly more predictive v alue at the 95% confidence level than ERPF or R20:3 alone, some statisticia ns suggest a 75% confidence level for adding an additional covariate to a m ultivariate model. Use of this level led to a model including both ERPF and R20:3. Conclusion: Single-sample ERPF measured in the immediate post-trans plant period, whether from OIH clearance or MAG3 clearance, was a statistic al predictor of graft survival for CD transplants. For MAG3, the peak time and R20:3 were also significant predictors. These associations held only fo r CD transplants and not for LRD transplants.