How do you diagnose temporal arteritis?

Ruling Out Temporal Arteritis (Giant Cell Arteritis)

To rule out temporal arteritis, perform a temporal artery biopsy, check ESR/CRP levels, and evaluate for characteristic clinical features including jaw claudication, temporal artery abnormalities, and age ≥50 years. 1

Diagnostic Algorithm

Step 1: Clinical Assessment

• Age: Patients ≥50 years have higher risk (positive LR 4.1) 1

• Key symptoms to evaluate:

  • Jaw claudication (positive LR 4.90) 2
  • Limb claudication (positive LR 6.01) 2
  • New-onset headache or change in headache pattern 1
  • Visual symptoms (diplopia, vision loss, amaurosis fugax) 3
  • Previous diagnosis of polymyalgia rheumatica (positive LR 2.07) 2

• Physical examination:

  • Temporal artery abnormalities:
    • Thickening (positive LR 4.70) 2
    • Loss of pulse (positive LR 3.25) 2
    • Tenderness (positive LR 3.14) 2
    • Beading or prominence 4

Step 2: Laboratory Testing

• ESR and CRP (both should be checked):

  • ESR >100 mm/h (positive LR 3.11) 2
  • ESR >50 mm/h (negative LR 0.48) 2
  • ESR >40 mm/h (negative LR 0.18) 2
  • CRP elevation (negative LR 0.38) 2
  • Caution: Normal ESR/CRP does not completely rule out GCA 5, 6

• Complete blood count:

  • Platelet count >400 × 10³/μL (positive LR 3.75) 2, 7
  • Elevated neutrophil-to-lymphocyte ratio and platelet-to-lymphocyte ratio 7

Step 3: Definitive Testing

• Temporal artery biopsy (gold standard) 2, 1:

  • Should be performed whenever GCA is suspected
  • Obtain adequate sample length (≥1 cm)
  • Unilateral biopsy is usually sufficient
  • Can remain positive for 1-2 weeks after starting glucocorticoids

• Imaging (when available):

  • Temporal artery ultrasound (88% sensitive, 97% specific) 2
  • Consider MR angiography or PET for large vessel involvement 1

Important Clinical Considerations

1. Do not delay treatment while awaiting biopsy results if clinical suspicion is high 2, 1

   • Start high-dose glucocorticoids (prednisone 40-60 mg/day) immediately
   • Consider IV methylprednisolone (500-1000 mg/day) for visual symptoms 1

2. Diagnostic pitfalls to avoid:

   • Relying solely on ESR/CRP (false negatives occur) 5, 6
   • Overvaluing headache and scalp tenderness alone (poor specificity) 2, 1
   • Delaying treatment while awaiting biopsy results 2
   • Failing to consider GCA in patients <70 years (though still possible) 2

3. When to refer urgently:

   • Patients with visual symptoms (risk of permanent vision loss) 1, 3
   • Patients with high-risk features despite normal inflammatory markers 6

4. Diagnostic criteria (American College of Rheumatology) 1:

   • Age ≥50 years at disease onset
   • New-onset headache
   • Temporal artery abnormalities
   • Elevated ESR (>50 mm/h)
   • Abnormal temporal artery biopsy

No single clinical feature or laboratory test is sufficient to completely rule in or rule out GCA, but the combination of clinical, laboratory, and pathological findings provides the most accurate diagnosis 1.