Claudin 18.2 Expression Concordance in Paired Cytology and Surgical Specimens of Gastric and Gastroesophageal Junction Adenocarcinomas.

While surgical specimens are standard for testing, the reliability of cytology specimens for CLDN18.2 assessment remains unclear.

At the cutoff of 75% or greater, cytology achieved 77% sensitivity, 92% specificity, 83% positive predictive value, and 88% negative predictive value.

In contrast, cases where one or both specimens were derived from metastatic sites showed lower agreement (PABAK = 0.68; bootstrap P < .01).

CONCLUSIONS.—: Cytology specimens could serve as a reliable source for CLDN18.2 biomarker testing when interpreted at the threshold of 75% or above.