Eliminating the Residual Negative Pressure in the Endoscopic Ultrasound Aspirating Needle Enhances Cytology Yield of Pancreas Masses.

Background: Prior to withdrawing the EUS-FNA needle from the lesion, the stopcock of the suction syringe is closed to reduce contamination. Residual negative pressure (RNP) may persist in the needle despite closing the stopcock.
Aims: To determine whether neutralizing RNP before withdrawing the needle will improve the cytology yield.
Methods: Bench-top testing was done to confirm the presence of RNP followed by a prospective, randomized, cross-over study on patients with pancreas mass. Ten milliliters of suction was applied to the FNA needle. Before withdrawing the needle from the lesion, the stopcock was closed. Based on randomization, the first pass was done with the stopcock either attached to the needle (S+) or disconnected (S-) to allow air to enter and neutralize RNP and accordingly the second pass was crossed over to S+ or S-. On-site cytopathologist was blinded to S+/S-.
Results: Bench tests confirmed the presence of RNP which was successfully neutralized by disconnecting the syringe (S-) from the needle. Sixty patients were enrolled, 120 samples analyzed. S+ samples showed significantly greater GI tract contamination compared to S- samples (16.7 vs. 6.7%, p = 0.03). Of the 53 patients confirmed to have pancreas adenocarcinoma, FNA using S- approach was positive in 49 (93%) compared to 40 using the S+ approach (76%, p = 0.02).
Conclusions: Despite closing the stopcock of the suction syringe, RNP is present in the FNA needle. Neutralizing RNP prior to withdrawing the needle from the target lesion significantly decreased GI tract contamination of the sample thereby improving the FNA cytology yield.
Clinical Trials Registration Number: NCT01995474.