Inter-rater variability of ultrasound scan measurements: balanced incomplete block design

Introduction To assess inter-rater variability of ultrasound scan measurements for determining period of gestation by three raters applying balanced incomplete block design.

Methodology Twelve pregnant women who attended the field antenatal clinics were subjected to scan measurements, in terms of bi-parietal diameter (BPD), femur length (FL), abdominal (AC) and head (HC) circumferences of the fetus between 15–24 weeks of gestation. Each pregnant woman was scanned by two of the three raters who were blind to the measurements made by the other using the same machine. Balanced incomplete block design was generated and data were analyzed using ANOVA.

Results There were no statistically significant variation among raters in measuring BPD (F = 0.68; p = 0.53), AC (F = 1.99; p = 0.19) and HC (F = 0.06; p = 0.94). There was statistically significant variation among raters for measuring FL (F = 7.4; p = 0.01).

Conclusion Statistically significant inter-rater differences were observed only for measurements of FL. However, despite the inter-rater differences of mean abdominal and head circumferences being not significant statistically, their variance can have a clinical significance.

DOI: http://dx.doi.org/10.4038/jccpsl.v15i1.4939

Journal of the College of Community Physicians of Sri Lanka Vol.15(1) May 2010 52-58