From the Guidelines
Diagnosing Polymyalgia Rheumatica (PMR) relies on a combination of clinical evaluation, laboratory tests, and imaging studies, with the most recent evidence suggesting that a diagnostic evaluation should include ESR, CRP, RF, anti-CCP, creatine kinase (CK) level, X-rays, and US of affected joints, as stated in the 2022 study 1. The diagnosis begins with a thorough medical history and physical examination, focusing on symptoms like bilateral shoulder and hip pain, morning stiffness lasting more than 45 minutes, and onset of symptoms typically in patients over 50 years old. Laboratory tests are essential, particularly erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), which are typically elevated in PMR patients, with ESR values often exceeding 40 mm/hour and CRP levels usually above 10 mg/L, as noted in the 2015 recommendations for the management of PMR 1. Some key points to consider when testing for PMR include:
- Complete blood count may show mild anemia of chronic inflammation
- Rheumatoid factor and anti-cyclic citrullinated peptide antibodies are typically negative, helping to distinguish PMR from rheumatoid arthritis
- Imaging studies can provide additional diagnostic information, with ultrasound often showing subdeltoid bursitis, biceps tenosynovitis, or glenohumeral synovitis, and MRI may reveal inflammation in shoulder and hip joints
- A dramatic response to low-dose corticosteroids (typically prednisone 10-20 mg daily) within 24-72 hours is considered a diagnostic criterion and therapeutic test, as mentioned in the 2022 study 1. It's also important to rule out giant cell arteritis and consider specialist referral, particularly in case of atypical presentation, as recommended in the 2015 European League Against Rheumatism (EULAR)/American College of Rheumatology (ACR) recommendations for the management of PMR 1.
From the Research
Diagnostic Methods for Polymyalgia Rheumatica (PMR)
The diagnosis of PMR is made primarily on clinical grounds, with no single diagnostic test available. However, several methods can be used to diagnose PMR, including:
- Clinical evaluation: Patients with PMR typically present with bilateral aching of the shoulder girdle, associated with morning stiffness, and may also experience neck and hip girdle pain 2.
- Laboratory tests: Elevated erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels are common in PMR, but normal values do not exclude the diagnosis 3, 4, 5.
- Imaging studies: Ultrasound and 18-fluorodeoxyglucose positron emission tomography associated with total body computed tomography (18-FDG PET/CT) may be useful in diagnosing PMR 4.
- Exclusion of other conditions: Other conditions that may mimic PMR, such as elderly-onset rheumatoid arthritis, must be excluded by appropriate testing and close monitoring of the disease course 2.
Laboratory Tests for PMR
Laboratory tests, such as ESR and CRP, can be used to evaluate disease activity and severity in PMR. However:
- ESR may be normal in some patients with PMR, particularly those with a younger age and less marked predominance of females 3.
- CRP values may be elevated in patients with PMR, even when ESR is normal 5.
- ESR and CRP values can be used to monitor disease activity and response to treatment, but are not definitive diagnostic tests 5, 6.
Clinical Criteria for PMR
Clinical criteria for PMR include:
- Bilateral shoulder and hip stiffness that is worse in the morning and improves with use 6.
- Elevated serum inflammatory markers, such as ESR and CRP 3, 2, 5.
- Absence of other conditions that may mimic PMR, such as elderly-onset rheumatoid arthritis 2.
- Response to glucocorticoid therapy, which is the mainstay of treatment for PMR 2, 6.