In order to determine observer variation in the assessment of the thyr
oid gland by ultrasonography, two specialists (one endocrinologist and
one radiologist) independently evaluated 76 thyroid glands, and asses
sed the sonogram as homogeneous, inhomogeneous, containing a solitary
solid lesion or a solitary cyst in each of 152 thyroid lobes. The obse
rved agreement between the two observers ranged from 0.80 to 0.91. By
the use of the kappa coefficient the observed agreement was adjusted f
or 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 2
2 lobes by the two observers; however, they only agreed on a classific
ation in 10 lobes (45%). Clinicians should be aware of the moderate ag
reement between observers in thyroid ultrasonography.