From the Guidelines
C-Reactive Protein (CRP) and erythrocyte sedimentation rate (ESR or sed rate) are essential inflammatory markers used to diagnose and monitor temporal arteritis (giant cell arteritis), with both tests typically elevated in active disease, as noted in a 2020 study 1.
Key Points
- ESR values often exceed 50 mm/hour and frequently rise above 100 mm/hour in temporal arteritis, while CRP levels are similarly elevated.
- These markers help clinicians assess disease activity and guide treatment decisions, particularly regarding corticosteroid therapy (typically starting with prednisone 40-60 mg daily) as recommended by the 2021 American College of Rheumatology/Vasculitis Foundation guideline 1.
- After initiating treatment, regular monitoring of CRP and ESR helps evaluate treatment response, with decreasing values indicating improvement.
- However, these tests are not specific to temporal arteritis and can be elevated in other inflammatory conditions, infections, or malignancies.
- Additionally, some patients (approximately 10-20%) may have normal inflammatory markers despite active disease, so normal results don't definitively rule out temporal arteritis.
- When monitoring disease activity during treatment tapering, these markers provide objective data to help prevent relapses, though clinical symptoms remain equally important in management decisions.
Diagnosis and Monitoring
The 2020 study 1 found that CRP level elevated had a sensitivity of 79.2% and specificity of 54.2% for diagnosing giant cell arteritis, while ESR elevated had a sensitivity of 82.6% and specificity of 33.8%. The 2018 update of the EULAR recommendations for the management of large vessel vasculitis 1 suggests that a suspected diagnosis of large vessel vasculitis should be confirmed by imaging or histology, and that regular follow-up and monitoring of disease activity is recommended, primarily based on symptoms, clinical findings, and ESR/CRP levels.
Treatment
The 2021 American College of Rheumatology/Vasculitis Foundation guideline 1 recommends early initiation of high-dose glucocorticoid therapy for induction of remission in giant cell arteritis, with the initial dose of prednisone typically being 40-60 mg daily. The guideline also suggests that adjunctive therapy, such as tocilizumab, may be used in selected patients with giant cell arteritis, particularly those with refractory or relapsing disease, or those at increased risk of glucocorticoid-related adverse effects.
From the Research
Role of CRP and Sed Rate in Diagnosing Temporal Arteritis
- C-Reactive Protein (CRP) and erythrocyte sedimentation rate (sed rate) are commonly used markers to aid in the diagnosis of temporal arteritis, but their role is not definitive 2, 3, 4, 5, 6.
- Elevated CRP and sed rate are often associated with temporal arteritis, but normal values do not rule out the disease 2, 4, 6.
- A study found that CRP was elevated in 10 of 11 patients with biopsy-proven temporal arteritis before treatment, and it was more sensitive than sed rate in following the adequacy of corticosteroid dosages 5.
Clinical Presentation and Diagnostic Challenges
- Temporal arteritis can present with a range of symptoms, including headache, temporal artery abnormalities, and visual symptoms, even with normal sed rate values 3, 6.
- The diagnosis of temporal arteritis is clinical, and a negative temporal artery biopsy or normal CRP and sed rate values do not exclude the disease 2, 6.
- Patients with classic clinical manifestations of temporal arteritis but with negative biopsy or normal laboratory values should be treated aggressively 2.
Laboratory Findings and Treatment
- Sed rate can be influenced by noninflammatory factors, and CRP may be a more reliable marker for monitoring disease activity and response to treatment 5.
- Even low-dose steroid therapy can lower sed rate values in patients with temporal arteritis, highlighting the importance of clinical correlation 3.
- Elevated CRP and sed rate values can return to normal with effective treatment, but this does not necessarily indicate complete resolution of the disease 5.