Observer variation in the scintigraphic diagnosis of solitary cold thyroid lesions

Observer variation in the clinical and laboratory evaluation of patients with thyroid dysfunction and goiter

Three endocrinologists assessed thyroid function (hypothyroid, possibly hypothyroid, euthyroid, possibly hyperthyroid, or hyperthyroid), thyroid size (small, medium, or large), thyroid type (diffuse, nodular, or solitary nodule), and diagnosis and treatment options in 55 patients (47 women and 8 men) with a median age of 43 years (range 19 to 74) suspected of thyroid disease. The observers were presented stepwise for the (1) patient, clinical examination, and patient history; (2) blood tests; (3) 99mTc-pertechnetate scintigraphy; and (4) ultrasonography. The reproducibility was assessed by means of the K coefficient. Compared with evaluation of the patient alone, agreement on thyroid dysfunction was almost perfect when the results of the blood tests were known. The K values for pairs of observers rose significantly from 0.55 to 0.65 to 0.88 to 0.93. All three observers altered their opinion as to thyroid dysfunction in one third of the patients when the blood tests were known. Compared with evaluation of the patient alone, agreement on the morphology of the thyroid gland did not improve significantly in spite of access to thyroid scintigraphy; with the addition of thyroid ultrasound, agreement improved significantly for some pairs of observers. The three observers agreed on the rough estimate of thyroid size in only 36% of the patients. When all information was available, the three observers agreed on diagnosis and treatment category in 60% of the patients. Doctors should bear in mind the considerable observer variation when they evaluate patients with suspected thyroid disease.

Observer variation in the interpretation of bone scintigraphy

To assess the reliability of bone scintigraphy, a random sample of 100 bone scans was reviewed twice by each of two physicians. Observer variation in the description and interpretation of bone scintigrams varied by diagnosis. Good to excellent k values were obtained for inter- and intraobserver variation in relation to metastasis or normal scans. For degenerative bone disease, as well as the specific agreement on major pathologies other than metastases, k values were found to be moderate. The agreement on the need for further radiographic studies was poor to moderate. The interpretation of bone metastases or normal scintigrams was found to be more reliable in a research setting than in the usual clinical framework, and the latter requires improvement. The interpretation of bone scintigraphy as consistent with degenerative changes is not reliable. The diagnosis should be evaluated by radiography.

Long-term follow-up of thyroid scintigraphies after 131I therapy of solitary autonomous thyroid nodules

The aim of the present study was to assess thyroid scintigraphies after 131I treatment of autonomous thyroid nodules with respect to evolution of the hot nodules as well as the extranodular tissue. A 99mTc pertechnetate scintigraphy was carried out 1-16 years (median 8 years) after 131I treatment of a solitary autonomous nodule in 66 patients remaining euthyroid. At the time of diagnosis, 9 of the patients were euthyroid and 57 were hyperthyroid, of whom 27 received antithyroid drug therapy prior to 131I treatment. The scintigraphies were evaluated twice by 4 specialists (3 endocrinologists and 1 specialist in nuclear medicine). There was total agreement between the 4 observers in 50 and 52% in the first and second evaluation, respectively. The interobserver variation was evaluated by means of omega coefficients and omega ranged from 0.18 to 0.76 indicating poor to substantial agreement. A solitary autonomous nodule with suppression of the extranodular thyroid tissue persisted in 50% of the patients, whereas a solitary cold nodule, homogeneous uptake or inhomogeneous uptake was found in 15, 22, and 13%, respectively. We conclude that although euthyroidism is achieved by radioiodine treatment, a hot nodule suppressing the 99mTc pertechnetate in the extranodular tissue is still found in 50% of the patients even when serum TSH has been normal for years. Antithyroid drug therapy prior to 131I treatment was more frequent in this group of patients.

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.