How Do You Make a Diagnosis of Gout Without Seeing MSU Crystals Under a Microscope?

How Do You Make a Diagnosis of Gout Without Seeing MSU Crystals Under a Microscope? Posted By:
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Primary care/urgent care/emergency rooms are all settings where acute monoarthritis is seen. The differential diagnosis includes acute crystal arthritis (gout, pseudogout), septic arthritis (rare), Lyme arthritis (clustered geographical locations), osteoarthritis, rheumatoid arthritis, and spondyloarthritis. Very few settings aspirate joints and send for culture and sensitivity, crystal analysis, cell count, and gram stain. Most do not have a microscope where they can observe crystals, and those that do may feel unqualified to accurately review slides looking for monosodium urate crystals (MSU).

So is there a way to make a diagnosis of gout (not pseudogout) without seeing crystals directly?

The American College of Rheumatology and the European League Against Rheumatism have developed an online calculator that will aid in diagnosis. Entry criteria include at least one episode of swelling, pain, or tenderness in a peripheral joint or bursa. The second question asks if MSU crystals have been identified by microscopy and, if so, then the calculator is not needed as the diagnosis has been made.

Then the questions are categorized into three domains: clinical, lab, and imaging. Items are listed in hierarchical order and are mutually exclusive, and the questions pop into the calculator as each one is answered. The calculator can be cleared after each patient is entered and can be printed for insertion into the patient's chart. Each domain should be scored for the highest category ever noted for the subject. A score of ≥8 classifies a subject as having gout.

I have used this for several patients and find it very helpful. Below is the link to the calculator. I would suggest you spend a few minutes playing with it to evaluate its potential for use in your clinical practice. goutclassificationcalculator.auckland.ac.nz

References
  • Aggarwal R, Ringold S, Khanna D, et al. Distinctions between diagnostic and classification criteria? Arthritis Care Res (Hoboken). 2015;67:891-897.
  • Neogi T, Jansen TL, Dalbeth N, et al. 2015 Gout classification criteria: an American College of Rheumatology/European League Against Rheumatism collaborative initiative. Ann Rheum Dis. 2015;74:1789-1798.
  • Neogi T, Jansen TL, Dalbeth N, et al. 2015 Gout classification criteria: an American College of Rheumatology/European League Against Rheumatism collaborative initiative. Arthritis Rheumatol. 2015;67:2557-2568.

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Filed under: Rheumatology

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