Investigation of reference interval for soluble st2 test in serum of vietnamese healthy persons

Authors:Thai Truc Linh, Phung Thi Quynh Giao, Luong Thi Hong Gam, Le Tu Ngoc Son, Nguyen Thi Thuy An, Nguyen Thi Le Huong, Le Ngoc Hung
Int J Biol Med Res. 2015; 6(3): 5184-5190  |  PDF File

Abstract

Objectives: The soluble ST2 isoform, sST2, has been classified as biomarker for myocardial fibrosis in 2013 ACCF/AHA Guideline for the Management of Heart Failure. There is an existence of differences in sST2 reference range with region and ethnicity. The aim of this study was the analytical validation of the Presage™ ST2 assay ELISA for quantification of sST2 in human serum and establishment of the sST2 reference range in serum of healthy Vietnamese peoples. Methods: We evaluated calibration curve, linearity, accuracy, precision, limit of quantification (LOQ), limit of detection (LOD) of analytical method, and analyte (serum) stability. The reference range of sST2 was determined from the 151 serum samples of healthy Vietnamese persons (73 males, 78 females). Results: The calibration curves of 7 points were fitted percentage of deviation (Dev%) < 4% and R2 equivalent to 1. The method was linear across the large measurement range, from 3 to 230 ng/ml. The coefficients of variation (CV%) of intra-day repeatability and total reproducibility of serum samples, <50, 100-199, and 200-300 ng/ml, were 13.6, 3.6, and 8.2% and 15.4, 14.3 and 11.0%, respectively. The accuracies of quality control samples varied from -7.3 to 3.1%. The LOQ and LOD were 3.82 and 1.67 ng/ml respectively. Recovery was evaluated by combining two QC samples with sST2 of 70 (high) and 23 ng/mL (low) in ratios of 7:3 and 3:7 (high:low); measured concentrations were 53.1 and 35.9 ng/mL, which were 95.0 and 96.8%, respectively of the expected concentrations. Recovery was also evaluated by combining two serum samples with sST2 of 118.9 (high) and 12.85 ng/mL (low) in ratios of 7:3 and 3:7 (high:low); measured concentrations were 78.3 and 41.9 ng/mL, which were 89.8 and 93.8%, respectively of the expected concentrations. The sST2 samples were stable for 72 h at room temperature, for 5 days at 2-8C, 2 continuous thawing/frozen times at 48h and 1 months at -20C. Concentration of sST2 samples were significantly higher in males compared to females (19.33±9.5 vs. 13.46±6.33 ng/ml; p<0.0001), and were not different by ages in males and by ages ≥ 30 yrs in females. In young females, 20-29 yrs, sST2concentrations were higher than those of other age-groups. Age-independent reference values, presented as empirical percentiles, were (2.5th-97.5th) 3.42-48.86 ng/mL in males, and 5.83-28.08 ng/mL in females. Conclusion: The Presage™ ST2 ELISA assay is fitted to quality specifications for measurement of sST2 in serum. The assay has a good precise, large linearity and low concentrations as 3 ng/ml. Reference range of sST2 are not different by age but are higher in males compared to females. Reference range of sST2 in Vietnamese peoples is similar to those of European populations but lower than that of US healthy population.