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The following is a summary of “Differential Impact of Hospitalization on Cystatin C– and Creatinine-Based Estimated GFR,” published in the March 2025 issue of Journal of the American Society of Nephrology by McCoy et al. 

Cystatin C and creatinine estimate GFR differently. The impact of hospitalization and persistence on eGFRdiff remains unclear. 

Researchers conducted a retrospective study to assess hospitalization’s impact on eGFRdiff (eGFRCys – eGFRCr). 

They analyzed 5,599 adults from the CRIC study with serum creatinine and cystatin C measurements. The study estimated the association of 6 hospitalization categories (0, <7, 7-<14, 14-<28, 28-<42, ≥42 days) with changes in eGFRCr, eGFRCys, and eGFRdiff between annual visits, assessing kidney function decline over time. 

The results showed that increasing hospitalization days were associated with greater declines in eGFRCys (e.g., -3.30 [95% CI -5.48, -1.13] ml/min/1.73m² for ≥42 days, P<0.001), while eGFRCr remained relatively stable (-1.12 [-2.77, 0.53] ml/min/1.73 m², P=0.21). This differential effect caused eGFRdiff to become progressively more negative with longer hospitalization (P<0.001). 

Investigators found that prolonged or repeated hospitalization led to larger decreases in eGFRCys compared to eGFRCr months after discharge. 

Source: journals.lww.com/jasn/abstract/9900/differential_impact_of_hospitalization_on_cystatin.582.aspx