What labs should be checked during a Polymyalgia Rheumatica (PMR) flare-up?

Laboratory Testing During PMR Flare-Up

During a polymyalgia rheumatica flare-up, check ESR and/or CRP as your primary inflammatory markers, along with a complete blood count, and reassess for steroid-related complications with glucose, creatinine, liver function tests, and bone profile. 1

Core Inflammatory Markers for Flare Assessment

• ESR is the single most useful laboratory parameter for assessing PMR disease activity during flares, though it can be normal in up to 48% of relapses 2
• CRP should also be measured, as it can be normal in up to 56% of relapses, making it slightly less sensitive than ESR for detecting flares 2
• Both markers should be checked together since neither alone is perfectly reliable—when one is normal, the other may be elevated 2
• High baseline ESR (>40 mm/1st hour) is associated with increased relapse rates and may indicate more aggressive disease requiring closer monitoring 1, 3

Essential Monitoring Labs During Flare

• Complete blood count to assess for anemia of inflammation and exclude other causes of symptoms 3
• Glucose to monitor for steroid-induced hyperglycemia, especially important during dose escalation for flare management 3
• Creatinine and liver function tests to ensure safe continuation or escalation of glucocorticoid therapy 3
• Bone profile (calcium, alkaline phosphatase) to monitor for steroid-induced bone loss, particularly relevant with prolonged or increased steroid exposure 3

Additional Testing in Specific Scenarios

• Consider serum amyloid A (SAA) if both ESR and CRP are normal but clinical suspicion for flare remains high, as SAA can be elevated when traditional markers are not 4
• Recheck rheumatoid factor and/or anti-CCP antibodies if the flare presents with atypical features such as new peripheral joint involvement, to exclude evolving rheumatoid arthritis 3, 5
• Creatine kinase should be measured if true muscle weakness (rather than pain-related functional limitation) develops, to exclude steroid-induced myopathy or inflammatory myositis 3, 5

Common Pitfalls to Avoid

• Do not rely solely on inflammatory markers to confirm or exclude a flare—nearly half of true relapses occur with normal ESR or CRP 2
• The absence of elevated inflammatory markers does not rule out PMR flare, particularly in younger patients, males, or those with longer symptom duration before diagnosis 4, 6
• Female patients have higher relapse rates and are more likely to require prolonged therapy, warranting more vigilant monitoring 1, 7
• "False positive" elevations of ESR or CRP are rare in PMR, so new elevations should prompt clinical reassessment for flare 2

Monitoring Schedule Context

• The EULAR/ACR guidelines recommend follow-up visits every 4-8 weeks in the first year and every 8-12 weeks in the second year, with additional visits indicated for suspected flares 1
• During a confirmed flare, increase monitoring frequency back to every 4-8 weeks until remission is re-established 1