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Article
April 1984

Usefulness of Synovial Fluid Analysis in the Evaluation of Joint EffusionsUse of Threshold Analysis and Likelihood Ratios to Assess a Diagnostic Test

Author Affiliations

From the Sections of General Medicine (Drs Eisenberg, Davidson, and Kaufmann) and Arthritis (Dr Schumacher), Department of Medicine, Hospital of the University of Pennsylvania and Philadelphia Veterans Administration Medical Center (Dr Schumacher), and the Leonard Davis Institute of Health Economics, University of Pennsylvania (Drs Eisenberg and Davidson), Philadelphia.

Arch Intern Med. 1984;144(4):715-719. doi:10.1001/archinte.1984.00350160063011
Abstract

• This study applied threshold analysis and likelihood ratios to determine the usefulness of a diagnostic test. Eleven staff rheumatologists or rheumatology fellows provided probability estimates for the most likely diagnoses both before and after synovial fluid analyses were performed on 180 patients with joint effusions. They also indicated whether the planned therapy was altered by the test results. The therapeutic thresholds and log likelihood ratios were derived for the six most frequent diagnoses. Synovial fluid analysis was most useful for patients likely to have gout, pseudogout, or infectious arthritis. The derived therapeutic thresholds were consistent with recommended medical practice, for example, with a lower threshold for possible septic arthritis (20%) than for possible gout (65%). This study demonstrates that threshold analysis and likelihood ratios can be used to assess the clinical contribution of diagnostic tests.

(Arch Intern Med 1984;144:715-719)

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