Title

Quality control (QC) in ultrasound fetal biometry: can self-scoring replace external QC?

Document Type

Article

Department

Obstetrics and Gynaecology (East Africa)

Abstract

Objectives: We have developed a comprehensive quality control (QC) policy of ultrasound for fetal biometry. The policy includes self-scoring of images and external / independent scoring. The hypothesis of this study was that self-scoring is high reproducible to the extent that it could replace external scoring.

Methods: The INTERGROWTH-21st study is a multicentre project assessing fetal growth currently underway in eight countries; it involves carrying out serial growth scans (15–42 weeks) (www.intergrowth21.org.uk). A part of the detailed QC policy involves qualitative analysis of acquired images. Sonographers are required to acquire images for the measurements of the fetal head circumference (HC), the abdominal circumference (AC) and the femur length (FL), and to score them according to validated scoring criteria. The maximum score is 6 for both the HC and the AC planes, and 4 points for the FL plane. In addition, 10% of all images are externally scored: they are reviewed and rescored at the coordinating unit at the University of Oxford, with reviewers blinded to study centre and sonographer. To test the hypothesis, agreement between local and the coordinating unit scoring was tested grouping the images scored (0–3 vs 4–6 for the HC and AC, and 1–2 vs 3–4 for the FL). An adjusted Kappa statistic was performed to account for the differences in prevalence between the two groups.

Results: A total of 12758 consecutive scans were included in the study from October 2009 to November 2012. The agreement between self-scoring and external scoring two scores was over than 95% for all image scores. Adjusted Kappas were respectively 0.981 (95%CI 0.947-1.015) for the HC, 0.989 (95%CI 0.962-1.015) for the AC, 0.979 (95%CI 0.944-1.015) for the FL.

Conclusions: There is a high level of agreement between local sonographers scoring their own images, and external scoring. This suggests that the QC protocol is highly reproducible; and that self-scoring can be used to complement external assessment.

Publication

Ultrasound in Obstetrics and Gynecology