Abstract:

Objective To evaluate the diagnostic performance of  estimated glomerular filtration rate (eGFR) based on serum creatinine (SCr) and serum cystatin C (CysC). Methods The concentrations of SCr and CysC were determined in 105 patients, whose GFRs were estimated by measuring 99mTc-DTPA clearance as the reference. Values of eGFR were calculated with eGFR algorithms recommended by Kidney Disease Improving Global Outcomes (KDIGO) guidance (2013 version). Diagnostic sensitivity, specificity, and likelihood ratios were calculated, and eGFR accuracies were assessed with receiver operator characteristic curve (ROC) analysis. Results When the cut-off values of the eGFR-SCr/CysC equation were 90, 60, and 45 mL/min/1.73 m2, the positive likelihood ratios (＋LR) were 9.3, 30.1, and 13 and the odds ratio (OR) were 21.1, 68.4 and 39.4, respectively, which reached satisfactory diagnostic performance. As eGFR-SCr/CysC cut-off point at 60 mL/min/1.73 m² with ＋LR at 30.1 and OR at 68.4, eGFR-SCr/CysC equation had the best diagnostic performance. The negative likelihood ratios (－LR) interval was 0.33-0.49, which had no value for diagnosis of chronic kidney disease (CKD). The diagnostic performance of eGFR-CysC equation was slightly better than eGFR-SCr equation. When the cut-off point was 60 mL/min/1.73 m², both the ＋LR and OR of eGFR-CysC and eGFR-SCr/CysC equations were the highest (20.8, 94.5, respectively), which were also helpful to confirm diagnosis of CKD. The combined-LRs (0.12-0.22) of eGFR were lower than separate-LRs (0.33-0.49) of eGFR, so the combined-LRs increased the ability of excluding diagnosis of CKD. Conclusion For evaluating the renal damage clinically, the eGFR-SCr/CysC equation is more accurate than the equation of SCr or CysC alone.

Key words: serum creatinine, cystatin C, chronic kidney disease, estimated glomerular filtration rate, receiver operator characteristic curve