CLINICAL EPIDEMIOLOGY III: JOURNAL APPRAISAL

Group 3February 11, 2010

Case Scenario

CA, 20, Female has an anterior cystic mass that started to grow in the area since she was 3 years old. The cystic mass is exactly at the midline at the level of the thyroid cartilage.

This is smooth, well circumscribed, non tender and moves up when the tongue is protruded.

Salient Features

• 20 y/o, female• Anterior cystic mass; exactly at midline, level

of thyroid cartilage• Smooth, well circumscribed, non tender and

moves up when the tongue is protruded

THYROGLOSSAL DUCT CYST

• often present as anterior midline masses in the 1st decade of life

• More than 25% of thyroglossal duct cysts present before the age of 5, and 40% present by the age of 10

• appear at a constant rate of almost 10% per decade in the ensuing years

• Diagnosis requires nothing more than a careful history and physical examination. A typically positioned mass that rises in the neck with swallowing or with protrusion of the tongue is diagnostic (Hechtman et al 2007)

• Confirmation of the thyroid in its normal location by palpation or demonstration by ultrasonography may be important to avoid incidental excision of a partially descended thyroid

The pre – test probability was set in 7% based on:

• Thyroglossal tract remnant occurs in 7% (which is usually asymptomatic) of the total population and only 20% occur at ages 20-30 years age.

• TTR/TDC is more common on pediatric patients which occur at around 30%.

• The incidence of ectopic thyroid tissue, misdiagnosed as a thyroglossal tract remnant, is probably between 1 and 2%, according to a series by Radkowski et al which makes our pretest probability much lower.

• Mostly thyroglossal duct cyst is diagnosed early and intervention is well established. Most adult patient at peak of around 4th decade has greater incidence for a malignancy.

Is there a role for ultrasonography in the pre-operative diagnosis of TDC?

• Population: thyroglossal duct cyst• Intervention: ultrasonography• Outcome: preoperative diagnosis• Methodology: retrospective cohort

• Search terms: – Thyroglossal duct cyst AND sonography AND

preoperative diagnosis

Article was obtained using the PUBMED

Article was obtained using the PUBMED

Article was obtained using the PUBMED

Article

CRITICAL APPRAISAL OF AN ARTICLE ON DIAGNOSIS

Was the objective of the study relevant to my clinical question?

YES.

RELEVANCE

VALIDITY GUIDELINES

Was there an independent comparison with a reference standard?

It was not stated in the article whether or not there was an independent comparison between sonography and the reference standard used, histopathology findings.

VALIDITY GUIDELINESDid the patient sample include the spectrum of

patients to whom the test will applied in practice?

YES. Although, there was no mention of the age range of the pediatric patients, all patients had cystic midline neck masses at the vicinity of the hyoid which is a characteristic of thyroglossal duct cysts.

VALIDITY GUIDELINES

Was the reference standard done regardless of the result of the test being evaluated?

YES. Pathological confirmation was done in all patients post-operatively.

VALIDITY GUIDELINESWere the methods for performing the test described in sufficient to permit replication?

YES.

OVERALL, Is the study valid?

YES. The study met most of the criteria for a valid study.

WHAT ARE THE RESULTS?

What were the likelihood ratios for the different possible test results?

Sensitivity: 99%Specificity: 95%LR (+): 19.8LR (-): 0.01

MANAGEMENTManagement will be dependent on which part of thespectrum the computed post test probability will fall

Computed post test probability:If positive for US = 1.58 / (1.58+1) = 60%If negative for US = 0.0008 / (0.0008+1) = 0%

RESULTS

Will the reproducibility of the test result and its interpretation be satisfactory in my setting?

There was no clear way of how the results were actually interpreted and how they were able to come up with the sensitivity and specificity of the test.

RESULTS

Are the results applicable to my patient?

YES. Since the disease is actually very rare and the findings of ultrasonography are highly specific, then it may be applied to our patient and although the age range of the patients (pediatric) is different from our patient (20 years old- adult), their clinical presentation is similar.

.

CLINICAL BOTTOM LINE

Ultrasound may be used as a pre-operativediagnostic tool for thyroglossal duct cysthowever the clinical findings may already

suffice.

RESOLUTION OF THE PROBLEM IN THE SCENARIO

Our patient, having all the classical findings ofthyroglossal duct cyst may therefore undergo

surgical intervention without the necessity of anultrasonography.