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SAT0189 Clinical utility of diagnostic tests for rheumatoid factor
  1. TM Madland1,
  2. E Ulvestad2,
  3. A Kaneström2,
  4. E Thomassen1,
  5. HJ Haga1
  1. 1Department of Rheumatology
  2. 2Department of Microbiology and Immunology, Haukeland University Hospital, Bergen, Norway

Abstract

Objectives To investigate and compare the accuracy and usefulness of diagnostic tests for rheumatoid factor (RF).

Methods In a cross-sectional study sera derived from patients admitted to the Department of Rheumatology were tested for presence of RF using both nephelometry and the Waaler test. Diagnostic sensitivity and predictive values of the tests were calculated and compared. The accuracy of tests was compared using receiver-operating characteristics (ROC) methodology.

Results Good agreement was found between the tests (kappa = 0.7). At cut-off 19 IU/mL nephelometry showed highest sensitivity (82.4%) and specificity (95.9%) for rheumatoid arthritis (RA). In comparison, the Waaler test had a sensitivity of 60.3% and specificity of 95.9% at cut-off titer 128. The tests showed nearly equal performance characteristics when predicting primary Sjögren`s syndrome (SS).

Conclusion Although both tests exhibit good performance characteristics, nephelometry has a higher accuracy when predicting RA. The common practice of using both tests for detection of RF is not recommended.

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