Public - Gout - Diagnosis

Gout	Author: Grace P. Teal, MD; Howard A. Fuchs, MD Editorial changes - 2009-09-02 Author information and module status



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Diagnosis
Use American College of Rheumatology criteria to establish the diagnosis if examination of synovial fluid or a suspected tophus does not confirm the presence of monosodium urate crystals. Perform arthrocentesis of the affected joint in patients without an established diagnosis who present with an acute swollen joint compatible with gout, for examination of the synovial fluid. Include cell count with differential as part of the synovial fluid examination in suspected gout. Aspirate a suspected tophus in patients without previous documentation of gout to establish the diagnosis. Consider radiography of a joint affected by gout to show abnormalities caused by gout or a concomitant process. Consider other disorders in the differential diagnosis of undiagnosed inflammatory arthritis.
History and Physical Examination Elements for Gout (table)
Laboratory and Other Studies for Gout (table)
Differential Diagnosis of Gout (table)


Use American College of Rheumatology criteria to establish the diagnosis if examination of synovial fluid or a suspected tophus does not confirm the presence of monosodium urate crystals.
Understand that joint pain and hyperuricemia do not establish the diagnosis. Attempt to aspirate synovial fluid (see information on arthrocentesis) or a tophus to detect monosodium urate crystals. Look for at least 6 of the following 12 American College of Rheumatology criteria for confirming the diagnosis of gout: Maximum joint inflammation within 1 day More than one attack over time Monoarticular arthritis (although gout can be polyarticular) Redness of joint Great metatarsophalangeal pain or swelling Unilateral great metatarsophalangeal involvement Unilateral tarsal involvement Suspected tophus Hyperuricemia Asymmetrical swelling within the joint on x-ray Subcortical cysts without erosion on x-ray Joint fluid culture negative for organisms during attack See table History and Physical Examination Elements for Gout
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Perform arthrocentesis of the affected joint in patients without an established diagnosis who present with an acute swollen joint compatible with gout, for examination of the synovial fluid.
Aspirate the affected joint and examine the synovial fluid for monosodium urate crystals in polymorphonuclear leukocytes by using a polarized microscope. Recognize that calcium pyrophosphate dihydrate crystals are also birefringent but diffract light differently and can be distinguished by that property. Look for bacteria on Gram stain and send the fluid for culture to exclude septic arthritis if suspicion is high. Note that aspiration of an affected joint during a subsequent attack may be appropriate if crystals are not initially documented in synovial fluid from patients with suspected gout. Realize that aspiration of relatively asymptomatic joints (e.g., nonpainful knee with effusion or swollen great metatarsophalangeal) may yield monosodium urate crystals and establish the diagnosis. See information on synovial fluid cell counts. See table Laboratory and Other Studies for Gout See figure Aspiration of the Knee from a Medial Approach. See figure Aspiration of the Ankle. See figure Aspiration of the Great Toe Joint. See figure Aspiration of the Wrist. See figure Tophaceous Material Viewed under Light Microscopy, Demonstrating Numerous Needle-Shaped Monosodium Urate Crystals. See figure Tophaceous Material Viewed under Polarized Microscopy, Demonstrating the Ability of Monosodium Urate Crystals to Bend Light. See figure Tophaceous Material Viewed under Polarized Microscopy with Color Compensator, Demonstrating Birefringence.
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Include cell count with differential as part of the synovial fluid examination in suspected gout.
Understand that joint fluid accumulations due to acute or chronic gout are nearly always inflammatory in nature, with leukocyte counts between 2000 and 75,000 cells/µL. Always exclude joint infection because there may be overlap between leukocyte counts in infection and gout. See table Classification of Joint Fluid to classify the type of joint fluid. See table Laboratory and Other Studies for Gout
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Aspirate a suspected tophus in patients without previous documentation of gout to establish the diagnosis.
Aspirate the tophus, after infiltrating the area with local anesthesia, using a sufficiently large needle (at least 22 gauge) to obtain a sample. Use polarized microscopy to examine the aspirate for monosodium urate crystals, but recognize that they will probably not be associated with polymorphonuclear cells because tophi tend to be acellular. If tophi are documented, begin treatment with appropriate uric acid-lowering agents (see section on drug therapy) to promote their dissolution. See table Laboratory and Other Studies for Gout
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Consider radiography of a joint affected by gout to show abnormalities caused by gout or a concomitant process.
Consider radiography in patients with gout, suspected gout, or an uncertain diagnosis to look for: Accumulated effects of inflammation, such as joint-space narrowing and destruction of the joint surface Evidence of tophaceous deposits Fracture or other joint processes listed in the table Differential Diagnosis of Gout See table Laboratory and Other Studies for Gout
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Consider other disorders in the differential diagnosis of undiagnosed inflammatory arthritis.
In considering the differential diagnosis of patients with inflammatory arthritis, use aspiration of an affected joint (see information on arthrocentesis) or suspected tophus to distinguish gout from other forms of inflammatory arthritis. See table Differential Diagnosis of Gout.
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FAQs

Grace P. Teal, MD (deceased) has no financial relationships with pharmaceutical companies, biomedical device manufacturers, or health-care related organizations. Howard A. Fuchs, MD, is a consultant for TAP Pharmaceuticals.
Steven E. Weinberger, MD, FACP, Acting Editor, PIER, has stock holdings in Glaxosmithkline and Abbott.

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