Auxiliary diagnosis of subepithelial lesions by impedance measurement during endoscopic ultrasound guided fine-needle biopsy.

Abstract

Endoscopic ultrasound guided fine-needle aspiration/biopsy (EUS-FNA/B) is the gold standard for diagnosing subepithelial lesions (SELs); however, its diagnostic ability for SELs <20 mm is low. We developed a new diagnostic method to differentiate between gastrointestinal stromal tumor (GIST) and non-GIST by measuring high-frequency impedance (H-impedance) using an EUS-FNB needle. The H-impedance of gastric epithelial neoplasms from 16 cases were measured using a conventional impedance probe to confirm whether H-impedance is clinically useful for assessing cell density (Study 1). The H-impedance values of exposed SELs from 25 cases using the conventional probe (Study 2) and non-exposed SELs from 20 cases using the EUS-FNB needle probe (Study 3) were measured to determine the diagnostic ability of H-impedance for differentiating GISTs from non-GISTs. H-impedance significantly positively correlated with cell density (P=0.030) (Study 1). The H-impedance of GIST (99.5) measured using conventional probe was significantly higher than those of the muscular layer (82.4) and leiomyoma (89.2) (P<0.01) (Study 2). The H-impedance of GIST measured using the EUS-FNB needle was also significantly higher than that of leiomyoma (GIST: 80.2 vs. leiomyoma: 71.8, P=0.015). The diagnostic yield of the impedance method for differentiating GISTs from non-GISTs had 94.4% accuracy, 88.9% sensitivity, 100% specificity, and 0.95 area under the curve. Diagnostic ability was not affected by lesion size (P=0.86) (Study 3). Auxiliary differential diagnosis between gastric GISTs and non-GISTs by the H-impedance measurement during EUS-FNB could be a good option especially when the lesion is smaller than 20 mm.