Evaluation of thyroid nodules – combined use of 99mTc‐methylisobutylnitrile scintigraphy and aspiration cytology to assess risk of malignancy and stratify patients for surgical or nonsurgical therapy – a retrospective cohort study
Objective Thyroid nodules are a common clinical problem, and differentiation between benign and malignant nodules is essential. The aim of this study was to evaluate an approach for cold thyroid nodules including 99mTc‐methylisobutylnitrile (MIBI) scintigraphy to assess risk of malignancy and stratify patients for therapy.
Design Retrospective cohort study; 391 patients with at least one cold thyroid nodule were consecutively admitted (between 1 January 2004 and 31 December 2006) and recommended for surgical or nonsurgical therapy.
Measurements Thyroid ultrasonography, 99mTc‐pertechnetate scintigraphy, laboratory tests, fine needle aspiration cytology (FNAC) and MIBI scintigraphy.
Results 57·3% (224/391) had one cold nodule, 17·9% (70/391) had several cold nodules, and 24·8% (97/391) had both cold and hot nodules. MIBI scintigraphy was classified into ‘positive’ (16·1%, 63/391), ‘weakly positive’ (19·2%, 75/391) or ‘negative’ (64·7%, 253/391). FNAC was classified into benign (87·9%, 247/281), nondiagnostic (6·8%, 19/281) or suspicious/malignant (5·3%, 15/281). 127 patients received surgery, revealing malignancy in 13·3% (17/127), predominantly papillary (64·7%, 11/17) and follicular carcinoma (23·5%, 4/17). MIBI scintigraphy was ‘positive’ (64·7%, 11/17) or ‘weakly positive’ (23·5%, 4/17) in most patients with malignant findings. FNAC was unavailable in 23·5% (4/17) with malignancy, positive in 38·5% (5/13) and negative in 61·5% (8/13). Among patients undergoing surgery, sensitivity, specificity, negative and positive predictive values for MIBI scintigraphy were 88·2%, 35·5%, 95·1% and 17·4%, for FNAC 38·5%, 90·6%, 90·6% and 38·5%, respectively, and for the combination (MIBI scan + FNAC) 92·3%, 30·6%, 96·3% and 16·9%. Benign MIBI‐positive nodules were predominantly follicular adenomas (68%, 33/48).
Conclusion Evaluation of cold thyroid nodules by MIBI scintigraphy aids therapeutic decisions: MIBI‐negative findings support nonsurgical management in about two‐thirds of patients, while MIBI‐positive findings have an increased risk of malignancy, supporting surgical therapy. However, the positive predictive value was low, which requires further research.
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Document Type: Research Article
Affiliations: 1: Practice for Nuclear Medicine, Klinikum Ludwigshafen, Ludwigshafen 2: Institute of Medical Biometry and Informatics, University of Heidelberg, Heidelberg, Germany
Publication date: May 1, 2012