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).

Table 1.

Proportion of Nodules Palpable by Size Category

First author, year (country)	Title	Patient population	Physical examiner	<1 cm	1–2 cm	>1.5 cm	>2 cm	All sizes
Brander, 1991 (Finland)	Thyroid gland: US screening in a random adult population	72 patients referred for suspected nodule or thyroid function disorder	Each patient examined by 1 or 2 examiners from a pool of 12 internists and residents	6.3% (1/16)	50.0% (14/28)	●	57.6% (19/33)	44.2% (34/77)
Witterick, 1993 (Canada)	Incidence and types of nonpalpable thyroid nodules in thyroids removed for palpable disease	60 consecutive patients who underwent thyroid surgery; no cervical adenopathy or previous thyroid surgery	Each patient examined by 2 of 3 experienced thyroid surgeons	●	●	●	●	58.1% (61/105)
Ezzat, 1994 (USA)	Thyroid incidentalomas. Prevalence by palpation and ultrasonography	100 healthy nonpregnant volunteers without previous ionizing radiation exposure or PH/FH of thyroid disease	Each patient had two examiners (not otherwise described)	●	●	●	●	31.3% (21/67)
Tomimori, 1995 (Brazil)	Prevalence of incidental thyroid disease in a relatively low iodine intake area	547 consecutive overweight, otherwise normal adults in urban relatively low-iodine intake area; excluded previous PH/FH of thyroid pathology	Not described	●	●	38.9% (7/18)	57.1% (4/7)	Φ
Schneider, 1997 (USA)	Thyroid nodules in the follow-up of irradiated individuals: comparison of thyroid ultrasound with scanning and palpation	Cohort treated with head/neck radiation for benign conditions between 1939 and 1962, normal examinations and scans; 22 high and 63 normal thyroglobulin	Not described	●	●	45.5% (5/11)	Φ	Φ
Wiest, 1998 (USA)	Thyroid palpation versus high-resolution thyroid ultrasonography in the detection of nodules	2441 (age range 6–72 years) clean-up workers from the Chernobyl incident	Each patient examined by 1 of 4 internists (2 board certified in nuclear medicine and radiology; 2 board certified/eligible in endocrinology)	16.7% (23/138)	20.2% (17/84)	40.0% (20/50)	48.1% (13/27)	21.3% (53/249)
% Palpable				6.3–16.7%	20.2–50.0%	38.9–45.5%	48.1–57.6%	21.3–58.1%

The last row shows the percentage of nodules detectable on ultrasound that were also palpated on physical examination. Φ Note that Tomimori et al. and Schneider reported palpability numbers only for nodules of a certain size, and so these counts are not included in the “All sizes” columns. The columns for nodule size are not mutually exclusive; for example, all nodules in the >2 cm column are also counted in the >1.5 cm column.

FH, family history; PH, personal history; US, ultrasound.

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.

Authors' Contributions

All authors contributed equally to the conception and objectives of the study and to writing and revising the main text. V.H. and N.A. performed review of literature and extraction of data. V.H. performed statistical analysis and created the main table. L.D. and D.O.F. oversaw the study and article writing as senior authors.

Author Disclosure Statement

No competing financial interests exist.

Funding Information

This study received funding from grant T32 DC009401 from the NIH/NIDCD (V.H.), 3R01CA251566-02S1 from the NIH/NCI (D.O.F., S.F.T.) and R01CA251566 to the University of Wisconsin.