It is important to realize with regard to the polymyalgia rheumatica diagnosis that there are these two points. First, one typical characteristic is a very high sedimentation rate and second, the patient’s blood has an elevated C-reactive protein.
Another key point is a surface antigen that the physician can snd for measurement with a special test. Specifically, it involves a white blood cell surface marker, called HLA-DR4, which these patients frequently have in their blood. Finally, in addition, the physician can send for another blood test to determine an elevated alkaline phosphatase.
Also, there may be an anemia, which can be measured in the blood of these patients. In research laboratories there may be more fancy tests such as looking for specialized T cell lymphocytes. The term for them is CD4 lymphocytes, which are immune cells specifically directed at the elastic membrane in the arterial walls of the cranial arteries in the case of giant cell arteritis.
The following table suggests tests that can be done to rule out other causes of muscle pains (from data of Ref. 1 and 2).
Tests to exclude other causes than polymyalgia rheumatica and temporal arteritis
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ESR (erythrocyte sedimentation rate) : very sensitive, but non specific. Also elevated in RA, SLE and infections
C-reactive protein : more specific, but also positive in other rheumatic illnesses.
TSH : to rule out hypothyroidism
monoclonal antibodies : to rule out multiple myeloma
EMG studies and muscle biopsy : positive in polymyositis, negative in polymyalgia rheumatica
temporal artery biopsy : can confirm giant cell arteritis histologically, but is negative in 33%!
CK (creatinine kinase) : this muscle enzyme is elevated in the blood with polymyositis, but not with polymyalgia rheumatica
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In the same fashion, apart from these diseases mentioned here, there are more rare other forms that your physician may want to rule out before diagnosing polymyalgia rheumatica.
References
1. ABC of rheumatology, second edition, edited by Michael L. Snaith , M.D., BMJ Books, 1999. Chapter 14.
2. The Merck Manual, 7th edition, by M. H. Beers et al., Whitehouse Station, N.J., 1999. Chapter 50.
3. Goldman: Cecil Textbook of Medicine, 21st ed.(©2000)W.B.Saunders
4. Ferri: Ferri’s Clinical Advisor: Instant Diagnosis and Treatment, 2004 ed., Copyright © 2004 Mosby, Inc.
5. Rakel: Conn’s Current Therapy 2004, 56th ed., Copyright © 2004 Elsevier
6. B. Sears: “The age-free zone”.Regan Books, Harper Collins, 2000.
7. B. Sears: “Zone perfect meals in minutes”. Regan Books, Harper Collins, 1997.
