Reducing inter-observer variation in thyroid volume calculation using a new formula and technique

Ultrasound (US) measurement of thyroid volume is used in diagnosis and follow-up of patients with thyroid disease. We assessed a new formula and technique for thyroid volume calculation, based on an automatically continuous trace transverse surface area (aTSA) calculation, to ascertain where this technique could reduce inter-observer variation.

Three observers with a different level of US expertise, using a 12-5 MHz linear transducer, examined 25 volunteers. Inter-observer variations were calculated for diameter measurements and for the thyroid lobe volume calculations using the single factor ANOVA method.

Using the new technique and formula, no statistically significant differences existed, in contradistinction to using the classical formula for an ellipsoid (P=0.02).

When thyroid volume measurements are required, we recommend using a new method of thyroid volume calculation based on the use of an automatically calculated continuous trace aTSA measurement to avoid significant inter-observer variation in calculation of thyroid lobe volumes.