Gout laboratory findings: Difference between revisions
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== Overview == | == Overview == | ||
A definitive [[diagnosis]] of gout is made from [[light microscopy]] of fluid aspirated from the joint | A definitive [[diagnosis]] of gout is made from [[light microscopy]] of the fluid aspirated from the joint. The fluid demonstrates [[intracellular]] negatively bi-refringent monosodium urate crystals and [[polymorphonuclear leukocytes]] in the [[synovial fluid]]. Although [[hyperuricemia]] is a common feature of gout, a high [[uric acid]] level does not necessarily mean a person will develop gout. | ||
== Laboratory Findings == | == Laboratory Findings == | ||
[[Hyperuricemia]] is a common feature; however, urate levels are not always raised.<!-- | [[Hyperuricemia]] is a common feature; however, urate levels are not always raised.<!-- | ||
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
A definitive diagnosis of gout is made from light microscopy of the fluid aspirated from the joint. The fluid demonstrates intracellular negatively bi-refringent monosodium urate crystals and polymorphonuclear leukocytes in the synovial fluid. Although hyperuricemia is a common feature of gout, a high uric acid level does not necessarily mean a person will develop gout.
Laboratory Findings
Hyperuricemia is a common feature; however, urate levels are not always raised.[1] Hyperuricemia is defined as a plasma urate (uric acid) level greater than 420 μmol/L (7.0 mg/dL) in males (or 380 μmol/L in females); however, a high uric acid level does not necessarily mean a person will develop gout. Urate is within the normal range in up to two-thirds of cases.[2] If gout is suspected, the serum urate test should be repeated once the attack has subsided. Other blood tests commonly performed are full blood count, electrolytes, renal function and erythrocyte sedimentation rate (ESR). This helps to exclude other causes of arthritis, most notably septic arthritis.
A definitive diagnosis of gout is made from light microscopy of fluid aspirated from the joint (this test may be difficult to perform) to demonstrate intracellular monosodium urate crystals and polymorphonuclear leukocytes in synovial fluid. The urate crystal is identified by strong negative bi-refringence under polarised microscopy and its needle-like morphology. A trained observer does better in distinguishing them from other crystals.
The level of complete blood count may be elevated in patients with gout. Blood chemistry including renal function and liver function need to be assessed before therapy.
References
- ↑ Sturrock R (2000). "Gout. Easy to misdiagnose". BMJ. 320 (7228): 132&ndash, 3. PMID 10634714.
- ↑ Siva C, Velazquez C, Mody A, Brasington R (2003). "Diagnosing acute monoarthritis in adults: a practical approach for the family physician". Am Fam Pghysician. 68 (1): 83&ndash, 90. PMID 12887114.