Observer variation in ultrasound assessment of the thyroid gland

In order to determine observer variation in the assessment of the thyroid gland by ultrasonography, two specialists (one endocrinologist and one radiologist) independently evaluated 76 thyroid glands, and assessed the sonogram as homogeneous, inhomogeneous, containing a solitary solid lesion or a solitary cyst in each of 152 thyroid lobes. The observed agreement between the two observers ranged from 0.80 to 0.91. By the use of the kappa coefficient the observed agreement was adjusted for change agreement. Kappa can vary from -1 (total disagreement) to +1 (total agreement) and kappa values between 0.55 and 0.60 were found. Among 152 lobes a solitary solid lesion, i.e. a nodule, was found in 22 lobes by the two observers; however, they only agreed on a classification in 10 lobes (45%). Clinicians should be aware of the moderate agreement between observers in thyroid ultrasonography.