Reliability of plastic cups to measure breast volume

Breast volume measurement is valuable in clinical practice, and various methods have been used. Nonetheless, no commonly accepted standard technique exists for clinical everyday use and there is no optimal method that is quick, cheap, minimally invasive, and acceptable for the patient and for the surgeon. Previously, a study has shown that the volume measured with plastic cups differed little from that measured from mastectomy specimens. The aim of the present study was to test the reliability of breast volume measurements with plastic cups as a tool to measure breast volume in everyday clinical practice. The plastic cups were designed by the senior author (AR) and comprise 14 cups from 125 millilitres (ml) to 2000 ml. Six raters measured 12 breasts on the same day. The results show that there is a certain variation between different raters, and that a certain rater seems to consistently measure slightly lower or higher volumes than the other raters. The Intra Class Correlation (ICC) coefficient of average measures between raters is 0.89, that is, the agreement between different raters is high. According to the Bland-Altman plot, the overall assessment of the comparisons of measurements between the different raters shows that the direction of the mean differences is close to zero. The limits of agreements of the differences were within ±56 ml. The coefficient of variation (CV) between different raters was 14%. Breast volume measurement with plastic cups is an easily usable quick and cheap way to measure breast volume in everyday clinical practice. The measurements have an acceptable reliability.