Development and Evaluation of Serum CST1 Detection for Early Diagnosis of Esophageal Squamous Cell Carcinoma

Purpose: Our pilot study has shown that cystatin SN (CST1) protein is highly expressed in esophageal squamous cell carcinoma (ESCC) tissues. We intend to develop a chemiluminescent enzyme immunoassay (CLEIA) available for serum CST1 detection and define the diagnostic value of CST1 detection for early ESCC patients, and establish a panel of CST1 with traditional tumor markers to improve the diagnostic sensitivity for early ESCC. Methods: Detection performance of CLEIA for CST1 was evaluated by linearity, detection limit, accuracy, precision, anti-interference and stability. Diagnostic performance of CST1 for early ESCC was evaluated by detecting CST1 of 112 early ESCC, 107 esophageal benign lesions (EBL), and 151 healthy controls (HC). CEA, CYFRA21-1 and SCC-Ag were detected by chemiluminescence immunoassay (CLIA). Results: The linear range and detection limit of CLEIA for CST1 were 6.25-400 pg/mL and 1.35 pg/mL, respectively; the average recovery rate was 102.65%; CVs of intra-batch precision and inter-batch precision were <1/4 TEa and <1/3 TEa, respectively; 8 interferents including 7 common interferents and CST4 had no interference on CST1 detection; stability evaluation showed good sample and reagent stability. The level and positive rate of CST1 in early ESCC group were significantly higher than those in EBL/HC groups (P 0.05). The diagnostic sensitivity of CST1 for early ESCC was 31.25% (specificity 92.64%, AUC 0.654). The diagnostic sensitivity of traditional tumor markers ranged from 16.07% to 28.57%, at 93.0% specificity, and SCC-Ag showed the highest AUC (0.709). Combination of CST1 and CEA, SCC-Ag exhibited the highest AUC up to 0.736 (sensitivity 49.11%, specificity 89.53%). Conclusion: CLEIA has excellent detection performance for CST1. CST1 might be a prospective serological biomarker for early diagnosis of ESCC, while combination of CST1 and CEA, SCC-Ag might improve the early diagnostic performance.