Aim. To assess standard and alternate laboratory markers of CKD in the early diagnosis of CKD in patients with chronic obstructive pulmonary disease (COPD).
Material and methods. The study comprised 226 patients of KCH № 2, who were allocated to four main groups depending on COPD severity (GOLD, 2014) and a control group. For all patients glomerular filtration rate (GFR) was estimated using both the creatinine-based CKD-EPI equation and cystatin C-based equation.
Results. When calculating GFR using creatinine-based equation, the percentage of COPD patients with normal GFR (>90 ml/min/1.73 m2) was significantly higher than for cystatin C-based equation (37.1 vs 12.6%, respectively; χ2=52.97, p=0.005). Patients with reduced glomerular filtration rate in the range of 59–45 ml/min/1.73 m2 had the opposite results. Among them the proportion of patients with normal GFR calculated by cystatin C-based equation was significantly higher (34.3 vs 1%, respectively; χ2=48.87, p=0.002). Similar results were seen in GFR declined to 44–30 ml/min/1.73 m2 (12.1% for cystatin C-based equation vs 0% for creatinine based equation; χ2=28.97, p=0.03) and to 29–15 ml/min/1.73 m2 (5.1% cystatin C-based equation vs 0% for creatinine based equation; χ2=5.13, p=0.045). In minimally decreased GFR (89–60 ml/min/1.73 m2) no significant differences were observed between the equations used for calculating GFR (51% for the creatinine vs 35.8% for cystatin C; χ2=2.95, p>0.05).
Conclusions. Cystatin C-based equation to estimate GFR is preferred for patients with COPD, as cystatin C is independent of muscle mass and anthropometric parameters.

Keywords: early diagnosis of CKD, co-occurrence of COPD and CKD, laboratory markers of CKD, renal dysfunction in patients with COPD, cystatin C