Negative pressure is not necessary for using fine-needle aspiration biopsy to diagnose suspected thyroid nodules: a prospective randomized study

Purpose: Fine-needle aspiration biopsy (FNAB) can be used to diagnose thyroid cancer and other tumors. Although FNAB without negative pressure (FNAB-P) reduces the risk of blood contamination, FNAB with negative pressure (FNAB+P) increases the sensitivity of the biopsy results. Therefore, we performed a randomized study of FNAB with or without negative pressure to identify the better diagnostic method. Methods: Between March 2016 and February 2017, 172 consecutive patients were enrolled to investigate >0.5 cm nodules with indeterminate or suspicious malignant features. Patients were randomly assigned to the FNAB+P group (a 50 mL syringe was used to provide negative pressure) or to the FNAB-P group (passive collection of blood in the needle's hub). The 2 methods' diagnostic adequacy and quality were evaluated using an objective scoring system. The study's protocol was registered with the World Health Organization Clinical Research Information Service (http://cris.nih.go.kr/cris, KCT0001857). Results: The patients were randomly assigned to the FNAB+P group (n = 86) or the FNAB-P group (n = 86). There were no significant intergroup differences in nodule position, size, age, consistency, calcification, BRAF mutation, or pathology. Evaluation of diagnostic adequacy parameters revealed no significant differences in background blood/clot (P = 0.728), amount of cellular material (P = 0.052), degree of cellular degeneration (P = 0.622), degree of cellular trauma (P = 0.979), or retention of appropriate architecture (P = 0.487). Furthermore, there was no significant intergroup difference in the diagnostic quality (P = 0.634). Conclusion: This prospective randomized study failed to detect significant differences in the diagnostic adequacy and quality of FNAB with or without negative pressure. Therefore, the examiner may select whichever FNAB method they prefer.