Clinical agreement between nurses in the ultrasound measurement of abdominal aortic diameter within a national screening programme

BACKGROUND: Accurate measurement is central to AAA-screening, but information concerning differences between-observers using modern ultrasound devices is lacking. Our aim was to assess clinical agreement among nurses within a national screening programme.

MATERIAL AND METHODS: Between-observer repeatability was assessed among two pairs of nurses (A&B; C&D) screening a consecutive series of men at a single community-clinic in Grampian, Scotland. All four nurses used the same ultrasound device (GE-LOGIQe 1.5-4.6 MHz curvilinear probe) to measure maximal infrarenal inner-to-inner (ITI) anteroposterior diameter in longitudinal and transverse planes. Nurses alternated in their measurements and were blinded to their partners' measurements. Participants remained supine whilst 'double-scanned'. Clinical agreement was assessed as twice the standard deviation (2SD) of mean differences. Analysis was undertaken using IBM-SPSS-Statistics (version 22) using the Bland-Altman 'limits of agreement' (95% LoA) approach (mean difference ±2SD) and related plots.

RESULTS: A total of 63 consecutive men underwent assessment (30 men by nurses A&B; 33 men by nurses C&D). Mean age 65.5 years, brachial BP 145/88 mmHg, current smokers 14%, never smoked 41%, diabetic 18%, arterial disease 11%, daily aspirin 16%, anti-hypertensives 35% and statin therapy 44%. Mean aortic diameter (ITI) was 1.81 cms (range 1.28 to 2.45; SD 0.18). Pooled mean differences between-nurses was 0.05 cms (95% CI 0.02 to 0.08); 2SD ±0.23 with 95% LOA -0.18 to 0.28 cms. Repeatability was similar in both planes and for both pairs of nurses.

CONCLUSION: Nurses can achieve a high level of agreement in the measurement of aortic diameter in a routine clinical setting.