Letter to the Editor: Sensitivity of Palpation for Detection of Thyroid Nodules with Attention to Size

Dear Editor:

Palpation of the thyroid is an examination skill routinely taught in medical school and remains a standard part of the physical examination in primary care, specialty care, and dental health maintenance visits (1). In general, thyroid palpation is intended to detect potentially malignant nodules.

It is not well established how effective palpation is at identifying thyroid nodules, and how nodule size affects the sensitivity of the examination. Thyroid nodules are reportedly palpable in 4–7% in the asymptomatic population and can be detected in up to 50–70% by ultrasound (2). There is also a significant false positive rate (palpation of a possible nodule without a correlate on ultrasound) of 68% (1).

We searched the scientific literature through the PubMed interface of MEDLINE for English-language scientific articles from 1985 to present for studies in which patients underwent both thyroid clinical examination and ultrasonographic assessment independently. Six articles published between 1991 and 1998 were identified and reviewed (3 –8). Two independent reviewers (N.A. and V.H.) extracted data from these studies, with disagreements resolved by consensus. Thyroid nodule size categories from individual studies were summarized to estimate the sensitivity of clinical examination in detecting thyroid nodules (Table 1).

In all, 21.3–58.1% of ultrasound detectable thyroid nodules were palpable, though data are sparse, with only two studies providing granular results by size (3,8). Reviewed data showed that 48.1–57.6% of large (>2 cm) nodules were not detected on clinical examination. Sensitivity worsened as nodule size decreased; only 6.3–16.7% of nodules <1 cm were found on neck examination.

Potential modifying factors for nodule detectability are worth mentioning. First, all six studies were published between 1991 and 1998, an era when palpation was the main detection modality for thyroid findings. Second, operator experience affects examination accuracy. Examiners in these studies included general practitioners, internists, surgeons, and board-certified endocrinologists with varying levels of expertise in thyroid disease (Table 1). Third, other factors including neck girth, obesity, sex, and position of the nodule within the thyroid were not considered in these studies and affect the likelihood of a nodule being palpable. Finally, we were limited by the relatively small subgroups for each size category, and not all size categories were examined in all studies.

Thyroid nodule palpation has a high false negative rate in detecting otherwise asymptomatic nodules, and many findings thought to be nodules have no sonographic correlate (1). Thus, physical examination of the thyroid gland has only limited utility as a screening test for nodules. These findings should be considered as thyroid gland diagnostic algorithms and physical examination purposes and goals are reviewed over time.