Substantial interobserver variation of thyroid volume and function by visual evaluation of thyroid (99m)Tc...

Area of Science:

• Endocrinology
• Nuclear Medicine
• Radiology

Background:

• (99m)Tc-pertechnetate scintigraphy is commonly used for evaluating patients with nodular goiter.
• The study aimed to assess the accuracy of visual estimation of thyroid radioactive iodine uptake (RAIU) and volume from scintigrams.

Purpose of the Study:

• To investigate the ability of experienced endocrinologists and nuclear medicine specialists to visually estimate thyroid 24-h (131)I uptake (RAIU) and thyroid volume from scintigrams.
• To evaluate the inter- and intraobserver agreement for these quantitative assessments.

Main Methods:

• Two endocrinologists and two nuclear medicine specialists visually evaluated thyroid scintigrams from 171 patients with nodular goiter.
• Assessments were performed in a blinded fashion, compared with true values, and repeated after four weeks.
• Kappa (κ ω) statistics were used to analyze inter- and intraobserver agreement.

Main Results:

• Observers had a low probability (6-22%) of correctly assessing thyroid RAIU and a low probability (14-22%) of correctly assessing thyroid volume.
• Endocrinologists tended to underestimate RAIU, especially when >30%. All observers underestimated thyroid volume when >80 ml.
• Low interobserver agreement was observed for both RAIU (κ ω: 0.03-0.43) and volume (κ ω: 0.19-0.48). Nuclear medicine specialists showed higher agreement than endocrinologists.

Conclusions:

• Thyroid (99m)Tc scintigraphy demonstrates poor interobserver agreement for quantitative assessments.
• Visual evaluation of scintigrams is inaccurate for determining thyroid RAIU and volume, even by experienced specialists.