Prognostic Value of Cystatin C in Pulmonary Embolism

Aim        To study a possibility of using serum concentrations of cystatin C (CYS) in early diagnosis and prediction of acute kidney injury (AKI) and associated in-hospital mortality and 30-day risk of death in pulmonary embolism (PE).Materials and methods        This study included 98 patients with suspected PE, of whom 63 had a confirmed diagnosis and formed the study group; the rest were excluded. CYS was measured on admission. The difference (CYSdiff) between the measured CYS and the estimated CYS corresponding to the glomerular filtration rate (GFR) of 75 ml/min/1.73 m2 was calculated using the reversed 2012 CKD-EPI Cystatin C formula. The estimated GFR was calculated as the difference between the CYS-based GFR (2012 CKD-EPI Cystatin C) and the creatinine-based GFR (2009 CKD-EPI). The 30-day mortality risk was assessed according to the ESC/ERS Guidelines for the diagnosis and treatment of acute PE in effect at the time of hospitalization.Results    AKI was diagnosed in 13 (21%) of 63 patients with PE aged 67±12 years, of whom 36 (57%) were men. In 7 (54%) cases, AKI was associated with chronic kidney disease (CKD), and in 6 (46%) cases, AKI developed for the first time. The measurement of the CYS concentration ensured early diagnosis and prediction of AKI with AUC=0.70 (95% confidence interval (CI) 0.57-0.81; p=0.009), optimal cutoff point (OP) >2.55 μg/ml (sensitivity 70%, specificity 62%), and AKI associated with CKD with AUC=0.78 (95% CI 0.65-0.88; p=0.001), OP >2.55 μg/ml (sensitivity 86%, specificity 62%). Similar predictive value for AKI was determined for CYSdiff: AUC = 0.70 (95% CI 0.57-0.81; p=0.009), OP >1.62 μg/ml with a sensitivity of 69% and specificity of 68%. Five patients (9%) died in hospital. The death rate was higher in AKI (χ2 = 5.8; p=0.018). CYS and CYSdiff levels did not predict in-hospital mortality (p >0.05 for both). The predictive value of eGFRdiff was unsatisfactory for either AKI or mortality (p >0.05 for both). It was found that CYS (AUC=0.76; 95% CI 0.63-0.85; p<0.001; OP>2.17 μg/ml) with a sensitivity of 70%, specificity of 70%, and CYSdiff (AUC=0.77; 95% CI 0.64-0.86; p<0.001; OP>1.22 μg/ml) with a sensitivity of 70%, and specificity of 70%, but not eGFRdiff were associated with a high 30-day risk of death (p=0.804).Conclusion            The study results confirm the effectiveness of CYS assessment in the early diagnosis and prediction of AKI, including cases associated with CKD. Prediction accuracy can be improved using CYSdiff. CYS levels do not predict in-hospital mortality but are associated with a high 30-day risk of death in patients with PE.