Preoperative Creatinine-to-Cystatin C Ratio and 1-year Risk of Infection-Related Hospitalization or Death with a...

Older kidney transplant recipients experience substantial early infection-related morbidity. The unscaled preoperative creatinine-to-cystatin C ratio (hereafter SI) is routinely available and may serve as an indirect laboratory-derived vulnerability marker for sarcopenia. We evaluated associations of SI with 1-year infection-related hospitalization and death with a functioning graft (DWFG).

We analyzed 497 recipients aged ≥65 years transplanted in 2017-2023 in a single-center analysis of a prospectively maintained database. SI used the last paired sample before induction immunosuppression. The primary endpoint was time to first infection-related hospitalization or DWFG within 365 days; components were analyzed separately. Cox models used prespecified adjustment and exploratory interactions by sex and pretransplant dialysis modality. Incremental value was evaluated by bootstrap-corrected discrimination, calibration, and Brier score.

Median age was 68.1 years; the full cohort included 312 men (62.8%) and 185 women (37.2%), with median SI 0.82 (IQR 0.70-0.95). The composite endpoint occurred in 182/497 (36.6%), infection-related hospitalization in 165/497 (33.2%), and DWFG in 29/497 (5.8%). Lower SI was associated with the composite (adjusted HR 1.32 per 1 SD decrease, 95% CI 1.09-1.60; p=0.004), infection-related hospitalization (HR 1.28, 95% CI 1.05-1.57; p=0.015), and, with greater uncertainty, DWFG (HR 1.62, 95% CI 1.04-2.52; p=0.034). There was no evidence of interaction by sex (p=0.86) or dialysis modality (p=0.91). Adding SI changed Harrell's C-index from 0.609 to 0.625 (Δ0.016; 95% CI -0.008 to 0.039).

In the entire cohort, lower preoperative SI was associated with a higher 1-year risk of the composite endpoint, which was driven mainly by infection-related hospitalization. SI is not a standalone risk-stratification tool, and prospective multicenter external validation is required before clinical implementation.