Point-of-Care Guides

Clinical Diagnosis of Gout Without Joint Aspirate

 


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Am Fam Physician. 2016 Sep 15;94(6):505-506.

Author disclosure: No relevant financial affiliations.

Clinical Question

Can gout be diagnosed with clinical and laboratory data, without performing joint aspiration?

Evidence Summary

Gout is a metabolic disorder of hyperuricemia in which excessive extracellular uric acid crystalizes and precipitates, causing end-organ damage, most commonly in joints. It is estimated that gout affects more than 8 million Americans and accounts for 7 million ambulatory visits in the United States annually.1 Gout is ideally diagnosed through identification of characteristic negatively birefringent crystals under polarized light microscopy in fluid aspirated from end-organ deposits, typically from a joint.2 However, fewer than 10% of patients with gout see a rheumatologist, and most cases of gout are diagnosed in the primary care setting based on signs, symptoms, and serum uric acid level.3 But how accurate is a clinical diagnosis, and can it be done better?

One study recruited 93 primary care physicians in the Netherlands who identified and referred 381 consecutive patients with acute monoarthritis.4 The researchers collected the physician's diagnostic impression of gout or nongout, a variety of signs and symptoms, and the serum uric acid level. They also obtained synovial fluid from each patient for monosodium urate crystal analysis. If the diagnosis was unclear, the patient was followed for a year and reevaluated using history, physical examination, and reaspiration. Gout was diagnosed in the 216 patients with monosodium urate crystals; 165 patients did not have gout, and instead had other arthropathies, such as rheumatoid arthritis, psoriatic arthritis, poststreptococcal reactive arthritis, Lyme arthritis, and osteoarthritis. Compared with the preferred diagnostic test, clinical diagnosis by a primary care physician demonstrated limited accuracy (sensitivity = 0.97; specificity = 0.28; positive predictive value = 0.64; negative predictive value = 0.87; positive and negative likelihood ratios = 1.3 and 0.1, respectively). Thus, a primary care physician's overall clinical impression is good at ruling out gout, but not at ruling it in.

The researchers then used logistic regression to identify the seven best independent predictors of gout.4  Each was assigned a point value according to how strongly it contributed to the diagnosis of gout (Table 1).4,5 Based on cutoffs of 4 points or less, 4.5 to 7.5 points, and 8 points or more, high and low scores had better positive and negative predictive values than the physician's overall impression: the positive predictive value was 80% with a high score vs. 64% with physician impression; the negative predictive value was 97% with a low score vs. 87% with physician impression.4

View/Print Table

Table 1.

Determining the Likelihood of Gout Using a Diagnostic Clinical Rule

Clinical variable

Points



Acute onset, with maximal symptoms within one day

0.5

Joint erythema

1.0

Hypertension or cardiovascular disease*

1.5

Male patient

2.0

Previous attack of arthritis or joint pain

2.0

First metatarsophalangeal joint is involved

2.5

Serum uric acid > 5.88 mg per dL (350 μmol per L)

3.5

Total score:

_____ (maximum: 13 points)

Derivation study 4

Validation study5


Total score

Number of patients in the score range (with gout/total)

LR

Number of patients in the score range (with gout/total)

LR

Suggested action

≥ 8 points: high risk

197/245 (80%)

3.1

141/162 (87%)

5.2

Diagnose gout

4.5 to 7.5: intermediate risk

17/63 (27%)

0.3

75/162 (46%)

0.7

Perform or refer for joint aspiration and polarized light microscopy analysis of crystals

≤ 4 points: low risk

2/72 (2.8%)

0.02

3/66 (4.5%)

0.04

Consider nongout diagnoses


LR = likelihood ratio.

*—Cardiovascular diseases include angina pectoris, myocardial infarction, heart failure, stroke, transient ischemic attack, and peripheral vascular disease.

†—Also based on a conversation with Steinberg and Janssens. (E-mail, June 12, 2016).

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, with additional information from reference 4.

Table 1.

Determining the Likelihood of Gout Using a Diagnostic Clinical Rule

Clinical variable

Points



Acute onset, with maximal symptoms within one day

0.5

Joint erythema

1.0

Hypertension or cardiovascular disease*

1.5

Male patient

2.0

Previous attack of arthritis or joint pain

2.0

First metatarsophalangeal joint is involved

2.5

Serum uric acid > 5.88 mg per dL (350 μmol per L)

3.5

Total score:

_____ (maximum: 13 points)

Derivation study 4

Validation study5


Total score

Number of patients in the score range (with gout/total)

LR

Number of patients in the score range (with gout/total)

LR

Suggested action

≥ 8 points: high risk

197/245 (80%)

3.1

141/162 (87%)

5.2

Diagnose gout

4.5 to 7.5: intermediate risk

17/63 (27%)

0.3

75/162 (46%)

0.7

Perform or refer for joint aspiration and polarized light microscopy

Address correspondence to Joshua Steinberg, MD, at jds91md@gmail.com. Reprints are not available from the author.

Author disclosure: No relevant financial affiliations.

REFERENCES

show all references

1. Hainer BL, Matheson E, Wilkes RT. Diagnosis, treatment, and prevention of gout. Am Fam Physician. 2014;90(12):831–836....

2. Wallace SL, Robinson H, Masi AT, Decker JL, McCarty DJ, Yü TF. Preliminary criteria for the classification of the acute arthritis of primary gout. Arthritis Rheum. 1977;20(3):895–900.

3. Owens D, Whelan B, McCarthy G. A survey of the management of gout in primary care. Ir Med J. 2008;101(5):147–149.

4. Janssens HJ, Fransen J, van de Lisdonk EH, van Riel PL, van Weel C, Janssen M. A diagnostic rule for acute gouty arthritis in primary care without joint fluid analysis. Arch Intern Med. 2010;170(13):1120–1126.

5. 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):609–614.

This guide is one in a series that offers evidence-based tools to assist family physicians in improving their decision-making at the point of care.

This series is coordinated by Mark H. Ebell, MD, MS, Deputy Editor.

A collection of Point-of-Care Guides published in AFP is available at http://www.aafp.org/afp/poc.



 

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