Risk Stratification of Thyroid Nodules Using the Thyroid Imaging Reporting and Data System (TIRADS): The Omission of Thyroid Scintigraphy Increases the Rate of Falsely Suspected Lesions

Abstract

Thyroid nodules are a common finding, especially in iodine-deficient regions. Ultrasonographic scoring systems such as Thyroid Imaging Reporting And Data System (TIRADS) are helpful in differentiating between benign and malignant thyroid nodules by offering a risk stratification model. Depending on the constellation or number of suspicious ultrasound features, a fine needle biopsy (FNB) is recommended. However, none of the previously published TIRADS considered the functional status of the nodules. Hyperfunctioning thyroid nodules (HTN) were presumed to exclude malignancy with a very high negative predictive value. Particularly in regions where the iodine supply is lower, the majority of HTN are seen in patients with normal TSH levels. Therefore, thyroid scintigraphy is essential for the detection of HTN. We investigated whether TIRADS identifies HTN as non-suspicious. We evaluated 615 HTN (23.2±10.0 mm at maximum diameter in 582 patients ( = 442 female, 57.7±13.2 years, and = 140 male, 60.1 ±12.7 years) detected byTc Pertechnetate or Iodine scintigraphy. Prior to evaluating the scintigraphic appearance, all nodules were analyzed prospectively with sonography, using the TIRADS model referenced in Kwak et al., wherein fine needle biopsy is recommended for TIRADS 4A or higher. We also investigated two subgroups, 42 nodules with available histology as well as 117 patients with subclinical or overt hyperthyroidism. Whereas 15.9% of the nodules were classified as TIRADS 3 or lower and <0.1% as TIRADS 5, most of the nodules were classified as TIRADS 4A (29.3%), 4B (29.3%), and 4C (24.9%), respectively. Altogether, more than 80% of the autonomous thyroid nodules were classified as TIRADS 4A or higher which would result in a recommendation of fine needle biopsy. Focusing on those 117 HTN that were already associated with hyperthyroid laboratory values, the rates were similar: 81.2% were categorized as TIRADS 4A or higher (4A: 33.3%, 4B: 29.9%, 4C:17.1%, 5: 0.9%). In the subgroup of patients who underwent thyroid surgery, all nodules were benign, confirming the known NPV of HTN with regard to malignancy exclusion. Integration of thyroid scintigraphy into the TIRADS model is essential to prevent unnecessary FNB and thyroid surgery.

Update 2019 zur MIBI-Szintigrafie bei hypofunktionellen Schilddrüsenknoten

“…Die meisten Schilddrüsenknoten weisen aber nur einen Teil dieser B-Mode-Kriterien auf und alle diese Einzelkriterien haben nur eine moderate Sensitivität und Spezifität zur Malignomdetektion [5,8,19]. Allerdings setzt sich die Beurteilung der Schilddrüsenknoten mithilfe der TIRADS-Einteilung zusehends durch [24,37,41,51] [2,22,24,34].…”

Prevalence of hyperfunctioning thyroid nodules among those in need of fine needle aspiration cytology according to ATA 2015, EU-TIRADS, and ACR-TIRADS

“…Recently, Schenke et al [19] investigated if TIRADS according to Kwak [20] identifies hyperfunctional thyroid nodules as non-suspicious. The study included 615 autonomous thyroid nodules in 582 patients with and without hyperthyroidism.…”

Ultrasound systems for risk stratification of thyroid nodules prompt inappropriate biopsy in autonomously functioning thyroid nodules

“…Consequently, variable indications are reported in the different clinical guidelines regarding the scintigraphic evaluation of thyroid nodules in the light of TSH 4,15 . It must also be considered that the sonographic features of AFTNs are heterogeneous 16,17 . In the presence of normal TSH levels, the likelihood of selecting these nodules for FNA might be high when TS is not performed and, even more disturbing, a significant number of indeterminate cytological reports might be expected in these cases 18 …”