Original Article: Differential Diagnosis of Polyarticular Arthritis
Issue Date: July 1, 2015
Available online at: https://www.aafp.org/afp/2015/0701/p35.html
to the editor: We appreciate this comprehensive and engaging article. We agree that joint fluid analysis is the preferred method for the diagnosis of gout, and that uric acid measurements are not beneficial when interpreted in isolation. However, as mentioned in an earlier article on gout published in American Family Physician,1 a diagnostic tool was developed in 2010 to aid primary care physicians in diagnosing the condition without the need for joint aspirate.2 This tool uses seven independent criteria, including serum uric acid level, to determine the likelihood that a patient is experiencing a gouty flare (Table 1).3 It was validated in a 2015 study, in which scores of 4 or less demonstrated a negative predictive value of 0.95, whereas scores of 8 or more had a positive predictive value of 0.87.3 Although scores between 4 and 8 may warrant joint aspiration and fluid analysis, this diagnostic tool may prove clinically useful when a gouty cause is suspected in patients with arthritic symptoms and the capability of joint aspiration does not exist or is impractical.
Table 1. Diagnostic Tool for the Evaluation of Suspected Gouty Arthritis
| Criteria | Points |
|---|---|
| Male | 2 |
| Previous self-reported arthritis attack | 2 |
| Onset within 1 day | 0.5 |
| Joint redness | 1 |
| Involvement of first metatarsophalangeal joint | 2.5 |
| Hypertension or at least one of the following conditions: angina pectoris, cerebrovascular accident, heart failure, myocardial infarction, peripheral vascular disease, transient ischemic attack | 1.5 |
| Serum uric acid level > 5.88 mg per dL (350 μmol per L) | 3.5 |
| Total | ____ (out of 13 possible points) |
note: Gout is unlikely with a score ≤ 4 (negative predictive value = 0.95); gout is likely with a score ≥ 8 (positive predictive value = 0.87). The probability of gout is uncertain with scores between 4 and 8, warranting further diagnostic testing or joint fluid aspiration.
Adapted with permission from Kienhorst LB, Janssens HJ, Fransen J, Janssen M. The validation of a diagnostic rule for gout without joint fluid analysis: a prospective study. Rheumatology (Oxford). 2015;54(4):612.
The views expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Department of the Army, Department of the Air Force, Department of Defense, or the U.S. government.
in reply: Thank you for bringing these articles to our attention. The decision tool may perform well when the typical and classic features of gout are present and may be especially valuable in resource-poor settings.1–2 However, its use is limited to straightforward cases. Synovial fluid testing remains indicated in patients with a mixed crystal arthritis, comprising both gout and pseudogout; when empiric gout treatment fails; or if there is a need for better informed decisions regarding newer generation uric acid–lowering agents, which are expensive and have considerable risks of other organ toxicity.3–4
