Clinical Agreement between Nurses in the Ultrasound Measurement of Abdominal Aortic Diameter within a National Screening Programme

Abstract

Accurate measurement is central to abdominal aortic aneurysm 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. Between-observer repeatability was assessed among 2 pairs of nurses (A & B and C & D) screening a consecutive series of men at a single-community clinic in Grampian, Scotland. All 4 nurses used the same ultrasound device (GE-LOGIQe 1.5-4.6MHz 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 while "double-scanned." Clinical agreement was assessed as twice the standard deviation (2 SD) of mean differences. Analysis was undertaken using IBM-SPSS-Statistics (version 22) using the Bland-Altman "limits of agreement" (95% LoA) approach (mean difference ±2 SD) and related plots. A total of 63 consecutive men underwent assessment (30 men by nurses A & B; 33 men by nurses C & D). Mean age 65.5years, brachial blood pressure 145/88mm Hg, current smokers 14%, never smoked 41%, diabetic 18%, arterial disease 11%, daily aspirin 16%, antihypertensives 35%, and statin therapy 44%. Mean aortic diameter (ITI) was 1.81centimeters (cm; range 1.28-2.45; SD 0.18). Pooled mean differences between nurses was 0.05cm (95% confidence interval 0.02-0.08); 2 SD±0.23 with 95% LoA -0.18 to 0.28cm. Repeatability was similar in both planes and for both pairs of nurses. Nurses can achieve a high level of agreement in the measurement of aortic diameter in a routine clinical setting.