Reproducibility of the SPI-US protocol for ultrasound diameter measurements of the Posterior Circumflex Humeral Artery and Deep Brachial Artery: an inter-rater reliability study

Elite overhead athletes are at risk of posterior circumflex humeral artery (PCHA) degeneration, aneurysm formation and thrombosis. Identification of the proximal PCHA and the nearby originating deep brachial artery (DBA) can be a challenge, even among experienced sonographers. The aim of this study was to assess the accuracy and precision of a newly designed standardized ultrasound (US) protocol (SPI-US) for assessment of the PCHA and DBA. Two experienced sonographers determined diameters of the PCHA and DBA using the SPI-US protocol. Inter-observer agreement was evaluated using intra-class correlation coefficient (ICC), standard error of measurement (SEM), minimal detectable change (MDC), Bland-Altman (BA) analysis, and variance component (VARCOMP) analysis. Thirty-three healthy volunteers participated. The ICC for diameter measurement of the PCHA and DBA were 0.70 (95 %CI 0.50-0.83) and 0.60 (95 %CI 0.30-0.80), respectively. The SEM for the PCHA and DBA was 0.32 mm and 0.29 mm and MDC was 0.90 mm and 0.80 mm, respectively. The BA and VARCOMP analyses showed no systematic and only marginal sonographer bias. The SPI-US protocol is accurate and precise for PCHA and DBA diameter assessment in cases where they originate from the axillary artery. PCHA and DBA diameter measurements are sonographer-independent using the SPI-US-protocol. • PCHA & DBA diameter assessment is accurate and reliable using the SPI-US protocol • PCHA & DBA diameter measurements are sonographer-independent using the SPI-US protocol • The SPI-US protocol minimal detectable change is 0.90 mm for PCHA diameter measurement • This minimal detectable change enables detection of PCHA aneurysms • First step towards international periodic surveillance of athletes at risk of PCHA-injury