Diagnostic Tests For Pseudogout

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[edit] Diagnostic Tests For Pseudogout

X-rays show a typical calcification of joint sufaces (articular cartilage) due to shedding of pyrophosphate crystals. This is called "chondrocalcinosis".

Samples under the polarized light microscope show the rhomboid, square or rod-shaped crystals, which makes the diagnosis (see also this image). Such samples are either obtained from centrifuged synovial fluid samples or from direct biopsies and can often also be found in white blood cells from the inflamed tissue.

As iron storage disease (hemochromatosis) can trigger pseudogout, a serum ferritin level would be desirable, if this is clinically suspected.

Other tests might include a TSH test to rule out hypothyroidism and occasionally a parathyroid hormone test, if there is an elevated serum calcium level and there is suspicion of a parathyroid adenoma. In the case of clinical evidence of amyloidosis the specialist might consider a rectal biopsy or a subcutaneous fat pad aspiration to do special staining tests and examination under a polarizing microscope to detect the characteristics of amyloid.

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References:

1. The Merck Manual, 7^th edition, by M. H. Beers et al., Whitehouse Station, N.J., 1999. Chapter 55.

2. ABC of rheumatology, second edition, edited by Michael L. Snaith , M.D., BMJ Books, 1999.

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