An explorative analysis on the optimal cryo-passes and freezing time of the ultrathin cryoprobe in endobronchial ultrasound-guided transbronchial mediastinal cryobiopsy
Sze Shyang Kho, Shirin Hui Tan, Chun Ian Soo, Hema Yamini Ramarmuty, Chan Sin Chai, Nai Chien Huan, Khai Lip Ng, Yuji Matsumoto, Venerino Poletti, Siew Teck Tie
Abstract
EBUS-guided transbronchial mediastinal cryobiopsy (TBMC) has emerged as a promising biopsy tool for diagnosing hilar and mediastinal pathologies. However, several fundamental technical aspects of TBMC remain unexplored. This study aims to determine the optimal number of cryo-passes and freezing time of the ultrathin cryoprobe in EBUS-TBMC concerning specimen size and procedural diagnostic yield. We conducted a retrospective chart review of patients with mediastinal and hilar lesions who underwent EBUS-TBMC between January 2021 and April 2023 across three hospitals in Malaysia. A total of 129 EBUS-TBMC procedures were successfully completed, achieving an overall diagnostic yield of 88.4%. Conclusive TBMC procedures were associated with larger specimen sizes (7.0 vs. 5.0 mm, p < 0.01). Specimen size demonstrated a positive correlation with diagnostic yield (p < 0.01), plateauing at specimen size of 4.1-6.0 mm. A significant positive correlation was also observed between the number of cryo-passes and both specimen size (p < 0.01) and diagnostic yield (p < 0.05). Diagnostic yield plateaued after 2-3 cryo-passes. In contrast, longer freezing times trended towards smaller specimens and lower diagnostic yield, though not reaching statistical significance. The highest diagnostic yield was recorded at the 3.1-4.0 s freezing time. The safety profile of TBMC remains favourable, with one case (0.8%) of pneumothorax and nine cases (7%) of self-limiting bleeding. In our cohort, TBMC performance with 2-3 cryo-passes and a 3.1-4.0 s freezing time to achieve a total aggregate specimen size of 4.1-6.0 mm appeared optimal. Further prospective studies are needed to validate these findings.