Blinded prospective comparison of the performance of 22-gauge and 25-gauge needles in endoscopic ultrasound-guided fine needle aspiration of the pancreas and peri-pancreatic lesions

Background: Both 22- and 25-gauge needles are used for endoscopic ultrasound (EUS)-guided fine-needle aspiration (FNA) of lesions, yet limited data exist on whether either offers an advantage over the other in terms of specimen cellularity and quality. Aim: The aim of this study was to compare sample quality for 22- and 25-gauge needles in EUS-guided FNA of pancreatic and peri-pancreatic lesions. Methods: Between October 2005 and June 2006, 12 patients with pancreatic or peripancreatic lesions underwent EUS-guided FNA with both 22- and 25-gauge Wilson-Cook Echotip needles. All procedures were performed with an Olympus linear echoendoscope by the same endoscopist to eliminate operator-dependent variability. Needle order was selected randomly, and two passes were made with each needle, consisting of ten uniform to-and-fro movements on each pass with 10-ml syringe suction. The specimens were immediately stained and independently reviewed by two cytopathologists, who were blinded to the needle used. Cellularity was graded as 0 to 6, with 6 being most cellular. Results: No statistically significant difference in cellularity was detected between the two needle size groups by cytologist 1 (mean difference, 0.04; 95% confidence interval [CI], -1.22 to 1.30; p = 0.94) or by cytologist 2 (mean difference, 0.2; 95% CI, -1.23 to 1.65; p = 0.76). When the data from both cytologists were combined, no significant difference in cellularity was detected between the two needle sizes (mean difference, 0.125; 95% CI, -1.22 to 1.47; p = 0.84). No significant difference in cellularity was detected between cytologists 1 and 2 (mean difference, 0.17; 95% CI, -0.15 to 0.48; p = 0.27). When the order in which needles were used was compared, no significant difference in cellularity was detected (p = 0.75). Three mechanical failures occurred with 25-gauge needles, but none occurred with 22-gauge needles. The visibility of the needles on EUS did not differ. Cytologic diagnoses were achieved in all cases: seven pancreatic adenocarcinomas, one pancreatic giant cell carcinoma, one pancreatic neuroendocrine tumor, one metastatic non-small cell carcinoma, one metastatic colon carcinoma, and one pancreatitis. There were no procedure-related complications. Conclusions: Both FNA needles provided accurate diagnoses in all patients. There was no significant difference between the 22- and 25-gauge needle groups in the independent interpretation of two cytopathologists with respect to cellular yield and ability to render a diagnosis.