Pseudogout (calcium pyrophosphate dihydrate deposition disease) causes an inflammatory arthritis that can be confused with gout. The International Association for the Study of Pain (IASP) reported criteria for its diagnosis.
Patient selection: acute or chronic pain in one or more joints
Common joints affected: wrists, symphysis pubis, knees
Criteria:
(1) presence of typical calcifications in the cartilage and synovial tissues seen on X-rays of an affected joint
(2) crystals consistent with calcium pyrophosphate dihydrate seen under compensated polarized light microscopy
(3) crystals consistent with calcium pyrophosphate dihydrate in synovial tissue by X-ray defraction
where:
• The crystals of calcium urate (gout) are negatively birefringent under compensated polarized light while calcium pyrophosphate dihydrate crystals are positively birefringent.
Criterion 1
Criterion 2
Criterion 3
Diagnosis
NA
NA
present
definite
present
present
NA
definite
present
absent
NA
probable
absent
present
NA
probable
absent
absent
absent
unlikely
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