From the Research
The average C-reactive protein (CRP) level in giant cell arteritis (GCA) is typically elevated, with values commonly ranging between 50-100 mg/L, though levels can sometimes exceed 100 mg/L in active disease. CRP is an acute phase reactant produced by the liver in response to inflammation, and its elevation reflects the systemic inflammatory nature of GCA. While CRP is a sensitive marker for GCA, it's not specific to this condition alone. Most patients with active GCA (over 80%) will have elevated CRP levels at diagnosis, making it a valuable screening tool when GCA is suspected. However, some patients with biopsy-proven GCA may have normal CRP levels (approximately 10-20% of cases), so a normal CRP does not exclude the diagnosis 1, 2. CRP levels typically decrease rapidly with effective corticosteroid treatment and can be used to monitor disease activity and treatment response 3, 4. Regular monitoring of CRP during treatment and tapering of steroids is recommended to detect potential disease flares. Some key points to consider in the diagnosis and management of GCA include:
- The clinical suspicion of GCA must be confirmed with a positive biopsy, even in cases with normal ESR and CRP levels 1.
- Color duplex ultrasonography is a noninvasive and useful method for supporting a diagnosis of temporal arteritis, with high sensitivity and specificity 1.
- The utility of ESR and CRP for the diagnosis of GCA has been evaluated, with CRP being a more sensitive marker than ESR for a positive temporal artery biopsy 2. It is essential to consider these factors when evaluating patients with suspected GCA, as they can impact diagnosis, treatment, and patient outcomes.