Background: Chronic obstructive pulmonary disease (COPD) and ischemic heart disease (IHD) frequently coexist, contributing to systemic inflammation and potential renal dysfunction. Cystatin C, a novel biomarker, may provide a more accurate assessment of glomerular filtration rate (GFR) in these patients compared to traditional creatinine-based methods.

Objective: To evaluate GFR using cystatin C in patients with COPD and comorbid IHD and compare it with creatinine-based estimations.

Methods: A cross-sectional study was conducted involving 120 patients diagnosed with COPD and IHD. Serum cystatin C and creatinine levels were measured, and GFR was estimated using the CKD-EPI cystatin C equation (eGFRcys) and the CKD-EPI creatinine equation (eGFRcr). Statistical analysis was performed using Pearson’s correlation and Bland-Altman plots.

Results: The mean eGFRcys (68.5 ± 12.4 mL/min/1.73 m²) was significantly lower than eGFRcr (74.3 ± 14.2 mL/min/1.73 m²) (p < 0.05). A strong correlation was observed between eGFRcys and eGFRcr (*r = 0.82, p < 0.001*), but Bland-Altman analysis revealed significant discrepancies, particularly in patients with severe COPD (GOLD stages III-IV).

Conclusion: Cystatin C-based GFR estimation may detect early renal impairment more effectively in COPD-IHD patients, suggesting its utility in comorbid conditions where muscle mass and inflammation affect creatinine metabolism.

COPD, ischemic heart disease, cystatin C

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