Usefulness of different ultrasound features of malignancy in predicting the type of thyroid lesions: a meta‑analysis of prospective studies

INTRODUCTION Thyroid nodules are a common medical problem. Thyroid ultrasound remains the most common method for preliminary evaluation and selection of nodules for fine‑needle aspiration biopsy (FNAB). Doppler examination and elastography are believed to improve the reliability of ultrasound in predicting malignancy.
OBJECTIVES The aim of this study was to evaluate diagnostic value of common ultrasound markers of malignancy of thyroid lesions.
MATERIALS AND METHODS The PubMed/MEDLINE and Cochrane Library databases were searched to identify studies meeting the inclusion criteria. The random‑effects model was used to calculate pooled odds ratio (OR), risk ratio, sensitivity, specificity, and positive and negative predictive values (PPV and NPV) of the individual features of thyroid malignancy on ultrasound. Only the prospective studies published between January 2007 and February 2013, performed using a transducer with the frequency of at least 7.5 MHz have been included in the meta‑analysis.
RESULTS The taller-than-wide shape of the thyroid nodule was shown to be the strongest predictor of malignancy (OR, 13.7; PPV, 76.0%); however, its sensitivity was 25.9%. Irregular margins and microcalcifications were also strong predictors of malignancy (OR, 7.2 and 7.1, respectively) and both had higher specificity (79.6% and 75.9%, respectively) than sensitivity (45.5% and 44.1%, respectively). Elastography of the thyroid gland also proved to be a valuable diagnostic tool in detecting malignant lesions (OR, 7.9). Hypoechogenicity, halo absence, and intranodular flow on a color Doppler examination were moderate predictors of malignancy (OR, 3.2, 3.8, and 4.3, respectively).
CONCLUSIONS Ultrasound features considered to be predictors of malignancy seem to be valuable for preliminary evaluation of thyroid nodules and referral for FNAB. However, they should always be interpreted with caution because none of them allows to reliably differentiate malignant from benign nodules.