Classification Tree for the Diagnosis of Temporal (Giant Cell) Arteritis

Temporal (Giant Cell) Arteritis can be diagnosed using a classification tree approach.

top level	second level	third level	fourth level	diagnosis
clinically abnormal temporal arteries	age at onset >= 50 years			TA
	age at onset < 50 years			non-TA
clinically normal temporal arteries	artery biopsy positive	age at onset >= 50 years		TA
		age at onset < 50 years		non-TA
	artery biopsy negative	claudication present	age at onset >= 50 years	TA
			age at onset < 50 years	non-TA
		claudication absent		non-TA

Surrogate criteria:

(1) If the clinical status of the temporal arteries is unknown, then the presence or absence of a tender scalp or scalp nodules may be used.

(2) If an artery biopsy is not available, then the presence or absence of a new headache may be used.

Criteria	Comment
age at disease onset >= 50 years	Occurs only rarely before the age of 50.
new headache	new onset or new type of localized pain in the head
temporal artery abnormality	temporal artery tenderness to palpation, or decreased pulsation, unrelated to arteriosclerosis of cervical arteries
claudication of jaw, tongue or on deglution	development or worsening of fatigue or discomfort in muscles of mastication, tongue or swallowing muscles while eating
abnormal temporal artery biopsy	Artery shows vasculitis with predominance of mononuclear cell infiltration or granulomatous inflammation, usually with multinucleated giant cells. The involvement is segmental, so an adequate biopsy is needed for diagnosis.
scalp tenderness or nodules	development of tender areas or nodules over the scalp, away from the temporal artery or other cranial arteries

Patient Subsets	Findings
TA patients	age >= 50 years at onset; clinically abnormal temporal arteries
	age >= 50 years at onset; artery biopsy positive; clinically normal temporal arteries
	age >= 50 years at onset; claudication; clinically normal temporal arteries; artery biopsy negative
non-TA patients	clinically normal temporal arteries; negative artery biopsy; no claudication
	age < 50 years at onset; claudication present; clinically normal temporal arteries; negative artery biopsy
	age < 50 years at onset; clinically normal temporal arteries; positive artery biopsy
	age < 50 years at onset; clinically abnormal temporal arteries

Performance:

• The sensitivity 95.3% and specificity 90.7%

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