From the Guidelines
To diagnose polymyalgia rheumatica (PMR), several key laboratory tests should be ordered, including erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), complete blood count (CBC), comprehensive metabolic panel, rheumatoid factor, anti-cyclic citrullinated peptide (anti-CCP) antibodies, thyroid function tests, and creatine kinase (CK) to rule out other conditions with similar presentations, as recommended by the 2015 European League Against Rheumatism (EULAR)/American College of Rheumatology (ACR) collaborative initiative 1. The following tests are essential for the diagnosis and management of PMR:
- ESR and CRP to assess inflammation
- CBC to evaluate for anemia of chronic disease
- Comprehensive metabolic panel to assess liver and kidney function
- Rheumatoid factor and anti-CCP antibodies to exclude rheumatoid arthritis
- Thyroid function tests to rule out hypothyroidism
- CK to exclude polymyositis and other myopathies Additional tests, such as temporal artery biopsy, ultrasound, and MRI, may be necessary in certain cases to exclude giant cell arteritis or other conditions that may mimic PMR, as suggested by the 2015 EULAR/ACR recommendations 1. It is crucial to note that the diagnosis of PMR should be based on a combination of clinical evaluation, laboratory tests, and imaging studies, and should be made in accordance with the 2015 EULAR/ACR recommendations, which emphasize the importance of a safe and specific approach to ascertain the PMR case definition 1.
From the Research
Diagnostic Tests for Polymyalgia Rheumatica
To diagnose polymyalgia rheumatica (PMR), several tests can be ordered, including:
- Erythrocyte sedimentation rate (ESR) 2, 3: This test measures the rate at which erythrocytes (red blood cells) settle in a test tube containing a blood sample and is used to assess inflammation in the body.
- C-reactive protein (CRP) 2, 3: This test measures the level of CRP in the blood, which is a protein that increases in response to inflammation.
- Ultrasonography 4: This imaging test can help diagnose PMR by showing bilateral subdeltoid bursitis.
Laboratory Parameters
Laboratory parameters such as ESR and CRP can be used to assess disease activity and severity in PMR 2, 3.
- ESR is a useful laboratory parameter in assessing PMR/GCA 2.
- CRP is a more sensitive indicator of current disease activity 3.
Diagnostic Criteria
The current diagnostic criteria for PMR include an ESR higher than 30 or 40 mm/1 hr 5. However, some patients with PMR may have a normal or slightly increased ESR at the time of diagnosis 5, 3.
- A subset of patients with PMR may have a normal ESR, characterized by a younger age, less marked predominance of females, longer diagnostic delay, and lower frequency of constitutional symptoms 5.
- CRP values can be elevated in patients with PMR, even if the ESR is normal 5, 3.
Screening for Giant Cell Arteritis
Screening for giant cell arteritis (GCA) is important in patients with suspected PMR, as PMR may be the first manifestation of GCA 4, 6.