Is an elevated C-Reactive Protein (CRP) a common finding in patients with Polymyalgia Rheumatica (PMR)?

Elevated CRP in Polymyalgia Rheumatica

Yes, elevated C-Reactive Protein (CRP) is a hallmark finding in polymyalgia rheumatica, with approximately 99% of patients showing elevated CRP at diagnosis, making it more sensitive than ESR for detecting active disease. 1, 2

Frequency and Diagnostic Value

• CRP is elevated in 99% of PMR patients at diagnosis, with only 1% presenting with normal values, making it an extremely reliable marker 2
• ESR is elevated in approximately 94% of cases, meaning 6% of patients present with normal ESR despite active disease 2
• When both markers are measured, inflammatory markers (ESR and/or CRP) are essential components of the diagnostic workup recommended by the European League Against Rheumatism 1

Clinical Significance of CRP Levels

• CRP is a more sensitive indicator of current disease activity than ESR, though ESR is superior for predicting relapse risk 2
• CRP values above 7.8 mg/dL at diagnosis independently increase the risk of relapse/recurrence (relative risk 2.1) 2
• High CRP levels are associated with more systemic signs and symptoms at presentation 2

When Inflammatory Markers Are Normal

• PMR with normal CRP is extremely rare (1% of cases) and should prompt consideration of alternative diagnoses 2
• When both ESR and CRP are normal (occurs in approximately 14% of cases), serum amyloid A (SAA) is typically elevated and can serve as an alternative inflammatory marker 3
• Patients with normal inflammatory markers tend to be younger at diagnosis, have longer symptom duration before diagnosis, and lower comorbidity rates 3
• Normal inflammatory markers do not exclude PMR or giant cell arteritis, and clinical presentation takes precedence over laboratory values 4

Monitoring During Treatment

• CRP normalizes rapidly with corticosteroid therapy, often before clinical symptoms fully resolve 5, 6
• During treatment, clinical symptoms should guide management more than CRP values alone, as corticosteroids suppress inflammatory markers 5
• CRP remains useful for monitoring, with repeat testing recommended every 4-8 weeks during the first year of treatment 1
• In refractory cases where CRP normalizes but symptoms persist, SAA may be a more potent therapeutic marker 6

Practical Algorithm for Interpretation

At diagnosis:

• Measure both ESR and CRP as part of the basic laboratory dataset 1
• If CRP is normal, strongly consider alternative diagnoses or measure SAA 3, 6
• CRP >7.8 mg/dL predicts higher relapse risk and may warrant closer monitoring 2

During treatment:

• Base dose adjustments primarily on clinical symptoms (pain, stiffness, functional status) rather than CRP alone 5
• If symptoms persist despite normal CRP on corticosteroids, consider measuring SAA 6
• Relapses can occur despite normal CRP, particularly in patients on immunosuppressive therapy 4