Individual ovarian volumes obtained from 2D and 3D ultrasound lack precision

Objective – To assess the precision of individual ovarian volume measurements by 2D and 3D transvaginal ultrasound scan. Study Design – Transvaginal 2D and 3D ultrasound examinations were performed on 49 women attending a tertiary centre for investigation or treatment for subfertility. Two observers calculated ovarian volume using both the prolate ellipsoid formula and virtual organ computer-aided analysis (VOCAL) with rotation steps of 30 degrees (3D-30). Results – For the four comparisons (inter- and intra-observer; 2D and 3D-30) we obtained intraclass coefficients of 0.97 to 0.98; and standard errors ranging from 17% to 14% (for inter-observer 2D and intra-observer 3D, respectively). The corresponding Coefficients of Repeatability ranged from 33% to 28%. Conclusions - Measurement of transvaginal ovarian volumes using both 2D and 3D ultrasound is imprecise for individuals. The imprecision is greater for lower ovarian volumes, which may be important in clinical practice. The average of two or more measurements is likely to be more accurate than a single measurement.