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Thyroid Disorders
Table 1: Ultrasound Characteristics Associated with combination of several ultrasound criteria together with clinical criteria
Thyroid Cancer
suggestive of malignancy will lead to a better selection of thyroid
nodules for FNAB.
35,36
Ultrasound Sensitivity Specificity Positive Negative
Characteristics (%) (%) Predictive Predictive
Value (%) Value (%)
According to the ATA guidelines, in the presence of a low or low to
Microcalcifications
1–5
26–59 86–95 24–71 42–94
normal serum TSH concentration, a radioiodine scan should be
Hypoechogenicity
2–5
27–87 43–94 11–68 74–94
performed and directly compared with the ultrasound images to
Irregular margins or 17–78 39–85 9–60 39–98
determine the functionality of each nodule larger than 1–1.5cm. The
no halo
2–5
AACE/AME and the ETA extend the indication to radioisotope scan,
Solid
4–6
69–75 53–56 16–27 88–92
suggesting that thyroid scintigraphy should be performed for a
Intranodule 54–74 79–81 24–42 86–97
multinodular goiter in iodine-deficient areas even if the TSH level is still
vascularity
3,6
in the normal range in order to identify the presence of an autonomous
The ability of single thyroid ultrasound criteria to predict malignancy has been summarized in
nodule. Concordance between the guidelines is very high for the
the recent consensus statement by radiologists. It documented low sensitivity and low
34 suggested actions even if the clinical evidence available for using
specificity for all single ultrasound criteria.
radioisotope scan is just fair (ATA: grade B; AACE/AME: grade B and C).
Table 2: Summary of Characteristics for Thyroid
Fine-needle Aspiration
Literature linked to the topic of thyroid scintigraphy is scarce. The ATA
guidelines quote no references, the ETA mentions one reference
Feature Mean (%) Range (%) Definition
(Pacini
37
), and the AACE/AME reports seven articles (one review and six
Sensitivity 83 65–98 Likelihood that patient with disease
observational studies). In fact, the quality of EBM evidence about the
has positive test results
use of radioisotope scans is quite low due to the absence of level 1 and
Specificity 92 72–100 Likelihood that patient without 2 evidence, and currently recommendations are based mostly on expert
disease has negative test results opinion and largely accepted thyroid practice.
Positive 75 50–96 Fraction of patients with positive test
predictive value results who have disease
FNAB is currently the most sensitive and specific test to distinguish
False-negative 5 1–11 Fine-needle aspiration negative;
benign and malignant thyroid nodules (see Table 2). For the further
rate histology positive for cancer
work-up of the example patient mentioned above, 74% selected FNA
False-positive 5 0–7 Fine-needle aspiration positive;
with ultrasound guidance. This seems surprising, considering that the
rate histology negative for cancer
nodule was easily palpable. However, as the vast majority of European
Fine-needle aspiration biopsy is currently the most sensitive and specific test to distinguish
26 experts use ultrasound for the initial investigation of such patients, it
benign and malignant thyroid nodules.
appears logical that they would also perform an ultrasound-guided FNA
evidence-based medicine (EBM) evidence in favor of clinical use rather than a palpation-directed FNA. Several recent reports suggest that
of ultrasound thyroid scan may be rated just as fair due to the absence ultrasound–FNA is more reliable than palpation–FNA.
26,38
With the use of
of level 1 and 2 clinical evidence. The examination of the linked ultrasound guidance, the sensitivity, positive predictive value, and
references confirms these remarks. For the thyroid ultrasound matter, negative predictive value of the test increase significantly. Accordingly, as
the ATA reports three observational studies (level of evidence: 3 the use of thyroid ultrasound by endocrinologists is becoming more
according to AACE scale), the ETA one retrospective observational study widespread, the AACE/AME guidelines suggest ultrasound FNA in the
(level of evidence: 3) and one consensus (level of evidence: 4), and the following clinical settings: any size nodule with a history of radiation,
AACE/AME five prospective observational studies (level of evidence: 3) family history of mycobacterium tuberculosis complex (MTC), or family
and six reviews (level of evidence: 4). For FNAB, the ATA reports three history of multiple endocrine neoplasia type 2 (MEN2); any size nodule
observational studies (level of evidence: 3), the ETA three observational with suspicious ultrasound features; nodules with extra-capsular growth
studies (level of evidence: 3) and one review (level of evidence: 4), and or cervical nodes; and impalpable or small (<1cm) nodule. The other two
the AACE/AME six observational studies (level of evidence: 3) and seven guidelines do not make specific recommendations for ultrasound-FNA.
reviews with a pooled analysis (level of evidence: 3–4). It is noteworthy
to observe that the evidence reported by the ATA, the ETA, and the If the FNA result is benign, 59 and 27% would ask this patient to return
AACE/AME guidelines on thyroid ultrasound and FNAB lacks in six to 12 months for thyroid palpation + ultrasound or thyroid
consistency. The three guidelines share only: palpation + ultrasound + FNA, respectively. The AACE/AME guidelines
suggest simple follow-up for cytologically benign thyroid nodules;
one reference in ATA and ETA (Marqusee et al.
31
); repeat ultrasound was not recommended. The ATA guidelines suggest
two references in ATA and AACE/AME (Tan et al.
32
and Hagag et al.
33
); clinical follow-up at six to 18 months, without ultrasound monitoring, for
and easily palpable benign nodules. Opinion on re-aspiration of benign
no references in the ETA Consensus and the AACE/AME GL. nodules remains divided. The AACE/AME suggests re-aspiration only for
enlarging nodules, recurrent cysts or nodules not shrinking after T4
In terms of the ability of thyroid ultrasound to predict malignancy, the therapy; the ATA guidelines suggest either re-aspiration or surgery for
recent consensus statement by radiologists documented low sensitivity growing nodules. Wiersinga has recommended repeat palpation and
and low specificity for all single ultrasound criteria,
34
as outlined in Table FNA one year after a benign FNA result.
39
Lucas et al. re-biopsied
1. However, as suggested by several studies, most likely the 116 patients with benign FNA and found no missed malignancy,
114 US ENDOCRINOLOGY
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