ABSTRACT
Lord SJ, Irwig L, Simes RJ. When is measuring sensitivity and specificity sufficient to evaluate a diagnostic test, and when do we need randomized trials? Ann Intern Med 2006; 144:850-5.
• Distinguish among primary, secondary or central, and tertiary or hypothalamic hypothyroidism • Assess the effectiveness of thyroxin suppression therapy • Identify patients in recovery from hypothyroidism • Distinguish resistance to thyroid hormone from the elevated thyrotropin (TSH) levels associated with
a TSH-secreting pituitary tumor
Contraindications to Testing • Critical illness or therapy with dopamine or glucocorticoids at high doses that suppress TSH pro-
duction
Alternatives to Testing • TSH surge test (see Test 2.7.2) in children with short stature and possible central hypothyroidism • Baseline sensitive TSH and free thyroxine (T4) assay (see Tests 1.1.1 and 1.1.3) alone in diagnosis
of hypothyroidism
Procedure 1. Obtain two baseline fasting blood samples, collected 20 minutes apart, for measurement of [TSH]
and [free T4]. 2. Pool equal aliquots of serum from each sample. 3. Administer TRH (Protirelin®; 500 mcg as an i.v. bolus), after baseline sampling. 4. Obtain blood samples for TSH testing at 15, 30, 45, and 60 minutes after the administration of TRH. 5. Assay of the 30-minute and 60-minute samples for [TSH] is usually adequate for diagnosis.
