Substantial interobserver variation of thyroid volume and function by visual evaluation of thyroid 99mTc scintigraphy

INTRODUCTION

^99mTc-pertechnetate scintigraphy is much used in the evaluation of patients with nodular goitre. We investigated the ability of experienced observers to estimate the thyroid 24-h ¹³¹I uptake (RAIU) and the thyroid volume by visual evaluation of the scintigram.

MATERIAL AND METHODS

Two endocrinologists and two nuclear medicine specialists visually evaluated thyroid scintigrams from 171 patients with nodular goitre. The variables were assessed in a blinded fashion according to predefined categories and then compared with the true values. The assessments were repeated after four weeks. Kappa (κω) statistics were used.

RESULTS

Low probability (range 6-22%) for the observers to assess the thyroid RAIU correctly. Probability of assessing the thyroid volume correctly in the 14-22% range. Endocrinologists underestimated the thyroid RAIU, mostly when RAIU
> 30%. All observers significantly underestimated thyroid volume > 80 ml. Low interobserver agreement for the thyroid RAIU assessment (κω: 0.03-0.43) and for the thyroid volume assessment (κω: 0.19-0.48). Corresponding κω for the intraobserver agreement were 0.34-0.68 and 0.37-0.62. Nuclear medicine specialists achieved a significantly higher agreement than endocrinologists evaluating parameters.

CONCLUSION

Thyroid ^99mTc scintigraphy has poor interobserver agreement and is inaccurate for assessment of quantitative thyroid parameters, even when performed by experienced specialists.

FUNDING

This study was supported by grants from the Danish Agency for Science, Technology and Innovation

TRIAL REGISTRATION

not relevant.

CORRESPONDANCE: Steen J. Bonnema. E-mail: steen.bonnema@dadlnet.dk

CONFLICTS OF INTEREST: Disclosure forms provided by the authors are available with the full text of this article at www.danmedj.dk

Reference: Dan Med J 2014;61(2):A4768