OBJECTIVES: To explore the reliability and validity of a recently developed instrument for assessment of ultrasound operator competence, the Objective Structured Assessment of Ultrasound Skills (OSAUS).

METHODS: Three groups of 10 doctors with different levels of ultrasound experience in obstetrics and gynecology were included. The novices had less than 1 month of experience, the intermediate group had 12-60 months of experience and the senior participants were all consultants. Fifteen participants performed transabdominal fetal biometry and the other 15 participants performed systematic transvaginal gynecological ultrasound scans. All scans were video-recorded and assessed by two blinded consultants using the OSAUS scale. The OSAUS scores were compared between the groups using the Kruskal-Wallis test, and pass/fail scores were determined using the contrasting-groups method of standard setting.

RESULTS: For the transabdominal fetal biometry examinations, the mean ± SD OSAUS scores of the novices, intermediates and senior participants were 1.5 ± 0.4, 3.3 ± 0.6 and 4.4 ± 0.4, respectively (P = 0.003). For the systematic transvaginal scans, the mean ± SD OSAUS scores of the novices, intermediates and senior participants were 1.8 ± 0.2, 3.1 ± 0.1 and 3.9 ± 0.5, respectively (P = 0.003). Post-hoc comparisons showed significant differences between each of the groups for both types of scans. The pass/fail score was 2.5 for the transvaginal scan and 3.0 for the transabdominal biometry examinations. The inter-rater reliability was 0.89.

CONCLUSIONS: Ultrasound competence can be assessed in a reliable and valid way using the OSAUS scale. The pass/fail scores may be used to help determine when trainees are qualified for independent practice.