Ultrasound follicle diameter measurement: an assessement of interobserver and intraobserver variation.

The intraobserver and interobserver variation of ultrasound measurement of Graafian follicles was assessed. Fourteen follicles from 10 to 30 mm in diameter were each measured three times in three orthogonal planes by three observers. The intraobserver standard deviation (SD) was 0.6 mm and interobserver SD, 1.2 mm, irrespective of follicle diameter. The pooled SD for both variables was 1.2 mm, giving 95% confidence limits of +/- 2.4 mm for any measurement.