[Role of Claudin-1 on diagnostic cut-off value and multiple tests in patients with papillary thyroid carcinoma]

Objective: To explore the diagnostic cut-off value of Claudin-1 (Cla-1) in papillary thyroid carcinoma (PTC) and the efficacy of the multiple test. Methods: Clinical and pathological data were collected from 295 patients with PTC and 137 patients with benign thyroid lesions (BTL) admitted to two hospitals in Pingdingshan City, Henan Province from January 2015 to June 2020. The expression index of Cla-1, the positive expression rate of high molecular weight cytokeratin (HMW-CK) and the negative expression rate of leukocyte differentiation antigen 56 (CD56) were calculated according to the results of immunohistochemistry. Receiver operating characteristic (ROC) curve was used to determine the cut-off value of Cla-1 for diagnosing PTC. Cla-1+HMW-CK, Cla-1+CD56, HMW-CK+CD56 and Cla-1+HMW-CK+CD56 were tested in series, and the diagnostic efficacy was evaluated by sensitivity, specificity and accuracy. Results: The age of PTC patients M (P₂₅, P₇₅) was 48.0 (41.0, 55.0) years old, among which 230 cases were male (78.0%). The age of BTL patients M (P₂₅, P₇₅) was 53.0 (46.0, 61.0) years old, including 34 males (24.8%). Cla-1 detection was conducted in all PTC and BTL patients, whereas only 198 and 97 cases conducted HMW-CK detection, 242 and 136 cases conducted CD56 detection, respectively. The M (P₂₅, P₇₅) of Cla-1 expression index in PTC was 80.0% (45.0%, 90.0%), which was higher than that in BTL [0.0 (0.0, 2.0%)] (P<0.001). The positive expression rate of HMW-CK was 93.9% (186/198) in PTC, and was negative in all BTL. The negative expression rate of D56 was 89.7% (217/242) in PTC, higher than that of BTL [1.5% (2/136)] (P<0.001). When expression index 19.0% was set as the cut-off value of Cla-1 for diagnosing PTC, the area under the ROC curve (AUC) was the maximum [AUC (95%CI): 0.981 (0.969, 0.994)], and the sensitivity, specificity and accuracy were 92.2% (272/295), 98.5% (135/137) and 94.2% (407/432), respectively. In multiple tests for diagnosis of PTC, the sensitivity ranged from 89.3% to 94.7%, specificity were all 100.0% and accuracy ranged from 93.1% to 96.9%. Conclusion: Cla-1 expression index ≥19.0% could be set as a cut-off value for the diagnosis of PTC and serial test of Cla-1 combined with HMW-CK(CD56) improves diagnostic specificity.