[Evaluation of intra- and interobserver agreement of Technetium-99m-sestamibi imaging in cold thyroid nodules]

A supplementary diagnostic tool in the assessment of cold thyroid nodules is scintigraphic imaging with^99mTc-MIBI. Aim of this study was to investigate the validity of this tool by determining the intra- and interobserver agreement in the assessment of cold thyroid nodules in Tc-MIBI scintigrams.

A retrospective study with 284 patients (16-85 years of age, 194 women, 90 men) was performed. They had at least one cold nodule and from each of whom were available at least one^99mTc-MIBI and the Tc- pertechnetate image. Eight physicians, active in nuclear medicine, reviewed the sctinti- grams twice in a random order. They were asked if they considered the combination a match, a mismatch, or inconclusive, and if the early or delayed image was more significant or if there was no difference.

Intraobserver agreement ranged from κ = 0.56 (moderate) to κ = 0.78 (substantial). Interobserver agreement ranged from κ = 0.44 to κ = 0.53 (moderate). Interobserver agreement for observers with more than 5 years of work experience in nuclear medicine ranged from κ=0.61 to κ = 0.70 (substantial), for observers with 2-5 years from κ = 0.53 (moderate) to κ = 0.61 (substantial) and for observers with < 2 years from κ = 0.47 to κ = 0.61. "No difference" was chosen in 70 resp. 77 % of all cases in session 1 resp. 2. The early image was preferred in 26 resp. 20 %, and the delayed one in 3 resp. 4 % of all cases.

The values of interobserver agreement of all eight observers show that the assessment of Tc-MIBI scintigrams is subject to a certain variance. Hence, they ought to be finally assessed by observers with at least 5 years of work experience.