Initial Workup for Suspected Giant Cell Arteritis
When GCA is suspected, immediately obtain ESR, CRP, and complete blood count with platelets, perform a focused physical examination of the temporal arteries, and assess for jaw or limb claudication—no single test rules in or out GCA, so proceed to temporal artery biopsy or vascular imaging for definitive diagnosis. 1, 2
Clinical History and Physical Examination
High-Yield Symptoms to Assess
- Jaw claudication (positive LR 4.90): Ask specifically about pain or fatigue in the jaw muscles with chewing that resolves with rest 1, 2
- Limb claudication (positive LR 6.01): Inquire about arm or leg pain with exertion, the strongest predictor of GCA 1, 2
- Headache: While common and important for prompting initial suspicion, headache alone has limited diagnostic value once specialist evaluation begins 1
- Visual symptoms: Document any vision loss, diplopia, or amaurosis fugax as these indicate ophthalmologic emergency 3
Critical Physical Signs
- Temporal artery thickening (positive LR 4.70): Palpate both temporal arteries for cord-like thickening 1, 2
- Temporal artery loss of pulse (positive LR 3.25): Compare pulses bilaterally 1, 2
- Temporal artery tenderness (positive LR 3.14): Assess for pain on palpation 1, 2
- Age >70 years: Absence of this feature decreases likelihood (negative LR 0.48) 1, 2
Laboratory Testing
Essential Initial Labs
ESR: Obtain immediately; absence of ESR >40 mm/h has negative LR 0.18, making GCA unlikely 1, 4
CRP: Superior to ESR with 90.1% sensitivity and negative LR 0.38 when <2.5 mg/dL 1, 4
Platelet count: Thrombocytosis >400 × 10³/μL has positive LR 3.75 1, 2
- Provides diagnostic value even before CRP/ESR results available 7
Interpretation Algorithm
If both ESR <40 mm/h AND CRP <2.5 mg/dL: GCA is unlikely but not excluded—proceed to imaging or biopsy only if high clinical suspicion based on jaw claudication, limb claudication, or temporal artery findings 1, 4
If ESR >40 mm/h OR CRP >2.5 mg/dL: Proceed to definitive testing regardless of other features 2, 4
Definitive Diagnostic Testing
Temporal Artery Biopsy
- Conditionally recommended over ultrasound as first-line confirmatory test 2
- Must be performed within 2 weeks of starting glucocorticoids to maximize diagnostic yield 2
- Remains gold standard despite ~77% sensitivity 1
Vascular Imaging
- Indicated for all newly diagnosed GCA patients to evaluate large vessel involvement 2
- Also indicated when temporal artery biopsy is negative but clinical suspicion remains high 2
- Options include ultrasound, MRI, CT, or PET 2
Critical Pitfalls to Avoid
- Do not wait for biopsy results to initiate treatment: Start high-dose glucocorticoids immediately when clinical suspicion is strong, as treatment delay risks irreversible vision loss 1, 2, 3
- Do not rely on headache alone: Once specialist evaluation is underway, headache has limited diagnostic specificity 1
- Do not use ACR 1990 classification criteria for diagnosis: These are for research classification, not clinical diagnosis 1
- Do not dismiss GCA with normal inflammatory markers: Up to 15% of cases have normal ESR, and rare cases have both normal ESR and CRP 5
- Obtain labs before starting steroids when possible: Pretreatment values have better sensitivity, though treatment should never be delayed for lab results 1, 4
Sequential Diagnostic Approach
- Immediate assessment: Platelet count and CRP provide fastest initial risk stratification 7
- ESR adds minimal value if platelet and CRP already obtained, though still recommended in guidelines 2, 7
- Proceed to biopsy or imaging for any patient with elevated inflammatory markers plus compatible clinical features 2
- Consider biopsy/imaging even with normal labs if jaw claudication, limb claudication, temporal artery abnormalities, or visual symptoms present 2, 4