Application of the European Kidney Function Consortium Equation to Estimate Glomerular Filtration Rate: A Comparison Study of the CKiD and CKD-EPI Equations Using the Korea National Health and Nutrition Examination Survey (KNHANES 2008-2021).

Background and Objectives: The European Kidney Function Consortium (EKFC) equation has been newly proposed for estimating glomerular filtration rate (eGFR) across the spectrum of age. We compared the EKFC equation with the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations in a large-scale Korean population. Materials and Methods: Using the representative Korean health examination data, the Korea National Health and Nutrition Examination Survey (KNHANES 2008-2021), the records of 91,928 subjects (including 9917 children) were analyzed. We compared the EKFC equation with CKiD, CKD-EPI 2009, and CKD-EPI 2021 equations and investigated their agreement across GFR categories. Results: In the total population, the CKD-EPI 2021 equation yielded the highest eGFR value, followed by the CKD-EPI 2009 and EKFC equations. In children, the distribution of eGFR differed significantly between the EKFC and CKiD equations (p < 0.001), with a wider range of eGFR values found with the CKiD equation. Each equation showed weak or moderate agreement on the frequency of the GFR category (κ = 0.54 between EKFC and CKD-EPI 2021; κ = 0.77 between EKFC and CKD-EPI 2009). The eGFR values found by the EKFC equation showed high or very high correlations with those by the CKiD, CKD-EPI 2009, and CKD-EPI 2021 equations (r = 0.85, 0.97, and 0.97, respectively). As eGFR values increased, bigger differences were observed between equations. Conclusions: This large-scale study demonstrates that the EKFC equation would be applicable across the entire age spectrum in Asian populations. It also underscores that national kidney health would be highly affected by an eGFR equation being implemented. Additional investigation and more caution would be warranted for the transition of eGFR equations.

Performance Assessment of Sysmex DI-60: Is Digital Morphology Analyzer Reliable for White Blood Cell Differentials in Body Fluids?

BACKGROUND: Few studies have evaluated digital morphology (DM) analyzers on body fluids (BF). We evaluated the performance of a DM analyzer, Sysmex DI-60 (Sysmex, Kobe, Japan) for white blood cell (WBC) differentials in BF samples. METHODS: In five BF samples (two pleural fluids and three ascites) containing a single, dominant cell type (>80%, neutrophils, lymphocytes, macrophages, abnormal lymphocytes, and malignant cells in each sample), we evaluated the precision of the DI-60 and compared the WBC differentials and turnaround times (TAT) between DI-60 and manual counting. RESULTS: The precision of the DI-60 pre-classification and verification was excellent (%CV, 0.01-3.16%). After verification, the DI-60 showed high sensitivity, specificity, and efficiency (ranges: 90.8-98.1%, 96.8-97.9%, and 92.5-98.0%, respectively) for the dominant cell types in neutrophil- and lymphocyte-dominant samples. For all samples, the DI-60 and manual counting showed high correlations for major cell types (neutrophils, lymphocytes, macrophages, and others, r = 0.72 to 0.94) after verification. The agreement between the pre-classification and verification of the DI-60 was strong in the neutrophil-dominant sample (κ = 0.81). The DI-60 showed a significantly longer TAT (min: s) than manual counting for all samples (median TAT/slide: 6:28 vs. 1:53, p < 0.0001), with remarkable differences in abnormal lymphocyte- and malignant cell-dominant samples (21:05 vs. 2:06; 12:34 vs. 2:25). CONCLUSIONS: The DI-60 may provide reliable data in neutrophil- and lymphocyte-dominant BF samples. However, it may require longer times and higher workloads for WBC differentials especially in BF samples containing atypical cells. Further improvement would be needed before applying DM analyzers for routine clinical practice in BF analysis.

Performance Evaluation of AFIAS ST2 and Ichroma ST2 Assays in Comparison with Presage ST2 Assay.

Background: Elevated soluble suppression of tumorigenicity 2 (sST2) levels may predict mortality in heart failure (HF) patients. The AFIAS ST2 assay (AFIAS ST2, Boditech Med Inc., Chuncheon, Korea) and ichroma ST2 assay (ichroma ST2, Boditech Med Inc.) are newly developed point-of-care (POC) assays for measuring sST2 level. We evaluated the performance of these assays, in terms of cut-off validation and prognosis, and compared them with that of the Presage ST2 assay (Presage ST2, Critical Diagnostics, San Diego, CA, USA). Methods: We validated the US FDA-claimed sST2 clinical cut-off of 35 ng/mL using 420 serum samples (298 samples from the universal sample bank of the American Association for Clinical Chemistry and 122 samples from reference individuals from Konkuk University Medical Center). We compared AFIAS ST2 and ichroma ST2 with Presage ST2, using 206 samples from patients with HF. We assessed prognosis using the three assays in 252 samples from the Barcelona ambulatory HF cohort subsets. Results: The upper reference limits of AFIAS ST2 and ichroma ST2 were within the clinical cut-off of Presage ST2. The results of AFIAS ST2 and ichroma ST2 were highly correlated with those of Presage ST2 (r = 0.82 and 0.81, respectively). Based on this cut-off, all three assays predicted cardiovascular death. Conclusions: The new POC assays, AFIAS ST2 and ichroma ST2, would be useful in clinical practice for managing HF patients, with performances equivalent to that of Presage ST2.