Background: Progressive reduction in acute rejection rates has led to an improvement of kidney graft survival throughout the first year, but long-term graft attrition rates remain stable beyond this point. Predicting the outcomes of kidney transplant recipients at 1-year would be useful in order to identify those for whom interventions may be needed. On one hand, it is known that allograft histology obtained by 1-year protocol biopsies is independently related to death-censored graft survival. On the other hand, several clinical risk scores, such as Kidney Transplant Failure Score (KTFS), have shown a good ability to predict long-term graft outcome. The aim of our study was to analyze the relationship between 1-year histologic findings of protocol biopsies and KTFS.
Methods/Materials: Between 2012 and 2016, 85 protocol biopsies were performed at 1-year post-transplant in our center and each biopsy was scored according to Banff criteria. KTFS was calculated taking into account 8 pre- and post-transplant clinical and analytical variables.
Results: Mean KTFS was 6.3 ± 1.7. KTFS related to t (r = 0.256, p = 0.018), i (r = 0.299, p = 0.005), ci (r = 0.326, p = 0.002), ct (r = 0.341, p = 0.001) and ah (r = 0.265, p = 0.014), but not with g, v, cg, cv, ptc  or mm. Mean KTFS values were higher in patients with higher scores of t (p = 0.046), i (p = 0.008), ct (p = 0.007) and ci (p = 0.009). After multivariate linear regression analysis, both i (β 0.507, 95%CI 0.011-1.004, p = 0.045) and ci (β 0.460, 95%CI 0.034-0.886, p = 0.035) related to higher KTFS, but only 14.7% of total variation in KTFS was explained by histologic scores.
Conclusion: A clinical scoring system predictive of long-term kidney graft survival such as KTFS relates to both acute and chronic histologic findings in 1-year protocol biopsies, although the degree of correlation was weak. Both clinical scores and histologic variables provide additional information to predict renal graft outcome.