Can ESR Be Low in PMR Patients Taking Prednisolone?
Yes, ESR can absolutely be low in a patient with polymyalgia rheumatica who is taking prednisolone, as corticosteroids suppress inflammatory markers including ESR. 1
Understanding the Effect of Prednisolone on ESR
Prednisolone directly suppresses the acute phase response, which means:
- ESR and CRP levels drop rapidly after initiating corticosteroid therapy, typically within days to weeks 2
- A normalized ESR during treatment does NOT exclude active PMR and should not be the sole criterion for treatment decisions 3
- The suppression of inflammatory markers is actually the expected therapeutic response, making ESR less reliable for monitoring disease activity once treatment has started 2
Clinical Implications for Diagnosis and Monitoring
If Prednisolone Was Started Before Diagnosis:
- This creates a diagnostic dilemma because the dramatic clinical response to steroids that helps confirm PMR has already occurred, and inflammatory markers are now artificially suppressed 1
- The patient may have PMR but now lacks the typical elevated ESR that would support the diagnosis 4, 5
- Consider measuring ESR/CRP before any dose changes if diagnostic uncertainty remains 6
If Prednisolone Was Started After Diagnosis:
- Low ESR during treatment is expected and appropriate - it reflects therapeutic response 2
- Clinical symptoms should guide management more than ESR values during the treatment phase 1
- EULAR/ACR guidelines recommend monitoring both ESR and CRP during follow-up, but emphasize that treatment decisions should be based primarily on clinical response, not laboratory values alone 6, 7
Important Caveats
A normalized ESR on prednisolone does not exclude complications:
- One case report documented biopsy-proven giant cell arteritis developing in a PMR patient whose ESR had normalized on low-dose corticosteroids 3
- If new symptoms suggestive of giant cell arteritis develop (headache, jaw claudication, visual symptoms), temporal artery biopsy should be performed regardless of ESR values 3
PMR can present with normal ESR even before treatment:
- Approximately 7-22% of PMR patients have normal or only slightly elevated ESR at diagnosis 4, 5
- These patients tend to be younger, more often male, and have less constitutional symptoms, but respond equally well to corticosteroids 5
- EULAR/ACR guidelines classify PMR with normal inflammatory markers as an atypical presentation warranting specialist referral 7, 8
Practical Approach
For monitoring patients already on prednisolone:
- Base treatment adjustments primarily on clinical symptoms (pain, stiffness, functional status) rather than ESR alone 1
- Follow-up intervals should be every 4-8 weeks in the first year, every 8-12 weeks in the second year 1
- ESR may rise again during disease flares or relapses, at which point it regains some monitoring value 7
- High baseline ESR (>40 mm/1st hour) before treatment predicts higher relapse risk and need for prolonged therapy 1, 6
The key principle: Once prednisolone is started, ESR becomes an unreliable marker because the drug itself suppresses it - clinical assessment becomes paramount 2