Key Points

Critical illness is known to acutely decrease eGFRdiff (estimation of GFR by cystatin C−estimation of GFR from serum creatinine [eGFRCr]), presumably because of loss of muscle mass falsely elevating eGFRCr.It is unknown whether this eGFRdiff effect occurs in all-cause hospitalizations and whether the effect persists after hospitalization.More hospitalization was associated with larger decreases in estimation of GFR by cystatin C compared with eGFRCr on measurements months after hospital discharge.

Background

Cystatin C has entered mainstream clinical care as a measure of kidney function, joining serum creatinine, which has been used for almost a century. However, many physicians notice that estimation of GFR from serum creatinine (eGFRCr) and estimation of GFR by cystatin C (eGFRCys) values can differ considerably. Hospitalization with critical illness is known to acutely decrease eGFRdiff (eGFRCys−eGFRCr). However, whether this effect occurs in all-cause hospitalizations and persists after hospitalization is unknown.

Methods

Among 5599 adult participants in the Chronic Renal Insufficiency Cohort study with serum creatinine and cystatin C measurements, we estimated the association of six categories of total days of hospitalization between annual study visits (never hospitalized, hospitalized

Results

Compared with no hospitalization between study visits, increasing days of hospitalization were associated with decreases in eGFRCys (e.g., −3.30 [95% confidence interval, −5.48 to −1.13] ml/min per 1.73 m2 for ≥42 days of hospitalization, test for trend P

Conclusions

Prolonged or repeated hospitalization was associated with larger decreases in eGFRCys compared with eGFRCr on measurements months after hospital discharge.