Analysis of false positive and false negative characteristics in the diagnosis of benign and malignant thyroid nodules with 99Tcm-MIBI scintigraphy

Abstract

Objective To analyze the radiological and pathological features of false positive and false negative diagnosis in thyroid nodules with 99Tcm -MIBI scintigraphy. Methods The clinical and pathologic data of patients who had received 99Tcm-MIBI imaging for thyroid nodules from January, 2015 to January, 2017 in the Department of Nuclear Medicine in Baoding No.1 Central Hospital were retrospectively analyzed, and 93 cases out of these patients were diagnosed by pathological examination. Visual observation was used for image analysis, and the criterion of interpretation was divided into positive, suspicious positive and negative, and all data were compared with pathological results. The diagnostic efficacy of 99Tcm -MIBI imaging was calculated and the clinical pathological features of false positive and false negative cases were analyzed. Results According to the 99Tcm-MIBI tumour scintigraphy positive/suspicious positive standards, the diagnostic sensitivity, specificity, accuracy, positive predictive value and negative predictive value were 87.50%(21/24), 53.62%(37/69), 62.37%(58/93), 39.62%(21/53) and 92.50%(37/40), respectively. The total incidence of false positive and false negative was 37.63%(35/93). The clinical parameters analysis of 99Tcm-MIBI imaging in benign thyroid nodules between true negative group and false positive group showed that the differences of gender, thyroglobulin (Tg), thyroglobulin antibody (TgAb) and thyroid peroxidase antibody (TPOAb) levels were not statistically significant, and the differences of age, diameter of nodule and pathological type were statistically significant (t=3.345, P=0.001; t=2.298, P=0.025; χ2 = 39.521, P=0.000) between two groups. The pathological types of pseudopositive nodular were nodular goiter (29/32), Hashimoto′s thyroiditis (2/32), and follicular adenoma (1/32). All false negative nodules were thyroid papillary microcarcinoma (3/3), and the diameters of all nodular were less than 1.0 cm. Conclusions The negative predictive value of 99Tcm -MIBI scintigraphy in diagnosing benign and malignant thyroid nodules is very high, and the negative predictive value is 100% for the diameter of nodules larger than 1.0 cm in this study. False positive results are more likely to occur in older patients and patients with larger nodules. Nodular goiter is more likely to produce false positive results in 99Tcm -MIBI scintigraphy. Key words: Thyroid nodules; Methoxyisobutylisonitrile; Radionuclide imaging; False positive; False negative