How is temporal arteritis diagnosed in an outpatient adult over 50?

Diagnosis of Temporal Arteritis in Outpatient Adults Over 50

Diagnose temporal arteritis (giant cell arteritis) in the outpatient setting through a combination of clinical assessment for key symptoms and signs, immediate laboratory testing (ESR and CRP), and confirmatory temporal artery biopsy or vascular imaging—but never delay treatment while awaiting diagnostic confirmation if clinical suspicion is high. 1, 2

Clinical Assessment: Key Symptoms to Identify

The diagnosis begins with recognizing specific clinical features that significantly increase the likelihood of GCA:

High-Value Symptoms (Positive Likelihood Ratios >2.0)

• Jaw claudication (pain with chewing): Most specific symptom with LR+ 4.90, present in ~50% of patients 1, 2
• Limb claudication: LR+ 6.01, though less common 1
• New-onset headache: Present in two-thirds of patients and up to 90% of biopsy-confirmed cases, though not statistically discriminating alone 2
• Visual disturbances (transient vision loss, diplopia, blurred vision): Occur in 20% before permanent blindness—this is an emergency 2
• Scalp tenderness: LR+ 3.14 1, 2

Important Demographic Factor

• Age over 70 years: Absence of this age (being younger than 70) has a negative LR of 0.48, making GCA less likely 1

Physical Examination: Temporal Artery Assessment

Examine the temporal arteries bilaterally for:

• Temporal artery thickening: LR+ 4.70—the most valuable physical finding 1
• Loss of temporal artery pulse: LR+ 3.25 1
• Temporal artery tenderness: LR+ 3.14 1
• Any abnormal temporal artery finding: LR+ 2.29 1

Laboratory Testing: Inflammatory Markers

Order these tests immediately in the outpatient setting:

Erythrocyte Sedimentation Rate (ESR)

• ESR >100 mm/h: LR+ 3.11 1
• ESR >80 mm/h: LR+ 2.79 1
• ESR >60 mm/h: LR+ 2.40 1
• ESR ≤40 mm/h: Negative LR 0.18—essentially rules out GCA 1
• Elevated ESR (>40 mm/h) is present in >95% of GCA cases 2, 3

C-Reactive Protein (CRP)

• CRP <2.5 mg/dL: Negative LR 0.38—makes GCA unlikely 1
• Normal CRP: Negative LR 0.40 1
• Elevated CRP is present in >95% of cases at diagnosis 2

Complete Blood Count

• Platelet count >400 × 10³/μL: LR+ 3.75 1

Critical caveat: While elevated inflammatory markers support the diagnosis, approximately 5% of GCA patients may have normal ESR/CRP, so do not exclude the diagnosis based solely on normal labs if clinical suspicion is high 2

Confirmatory Testing: Biopsy or Imaging

Temporal Artery Biopsy (Gold Standard)

• Obtain a specimen ≥1 cm in length, performed by an experienced surgeon and evaluated by an experienced pathologist 1, 2, 4
• Look for: arterial wall thickening, narrowed lumen, mononuclear inflammatory cells invading the media, and occasionally multinucleated giant cells 1, 3
• Important: Biopsy can remain positive for up to 2 weeks after starting corticosteroids, so do not delay treatment to obtain biopsy 1, 2
• Negative biopsy does not exclude GCA due to skip lesions 5

Vascular Imaging (Alternative or Adjunctive)

When biopsy is unavailable, contraindicated, or negative despite high clinical suspicion:

• Temporal artery ultrasound: Look for "halo sign" (circumferential arterial wall thickening) 1, 2, 4
• MR or CT angiography: Evaluate for large vessel involvement in neck/chest/abdomen/pelvis 2
• PET-FDG: Shows increased tracer uptake in arterial walls 1

Diagnostic Algorithm

1. Suspect GCA in any patient >50 years with new headache, jaw claudication, visual symptoms, or scalp tenderness 1, 2

2. Immediately order: ESR, CRP, CBC with platelets 1, 2

3. Perform focused physical exam: Palpate temporal arteries bilaterally for thickening, tenderness, or absent pulse 1

4. If high clinical suspicion (jaw claudication + elevated ESR/CRP, or visual symptoms):

   • Start high-dose corticosteroids immediately (40-60 mg prednisone daily) without waiting for confirmatory testing 1, 2
   • Arrange urgent temporal artery biopsy (within days) or vascular imaging 1, 2

5. If moderate suspicion: Arrange temporal artery biopsy or ultrasound before starting treatment, but do not delay beyond 1-2 days 1

6. If low suspicion (normal ESR <40 mm/h AND normal CRP AND age <70): Consider alternative diagnoses 1

Common Pitfalls to Avoid

• Do not wait for biopsy results to start treatment if clinical suspicion is high—permanent vision loss can occur rapidly 1, 2, 6
• Do not rely on headache alone—it lacks diagnostic specificity despite being common 1
• Do not exclude GCA based on normal inflammatory markers alone in patients with compelling clinical features 2
• Do not use the 1990 ACR classification criteria for clinical diagnosis—these were designed for research, not clinical practice 1
• Recognize atypical presentations: 40% present with fever of unknown origin, respiratory symptoms (especially dry cough), or large artery involvement without cranial symptoms 7