Cusato and Bush raise concerns regarding the accuracy of diagnosis, bias introduced by knowledge of rheumatoid factor (RF) status during chart review, and inclusion of patients without joint complaints in our study of the RF's clinical utility.1 The "gold standard" for diagnosis of rheumatoid arthritis (RA) (the American College of Rheumatology criteria) has always been a major obstacle in assessing the utility of tests in this illness because they may be unreliable (eg, morning stiffness is subjective; there may be significant interobserver variability in the assessment of arthritis) and, perhaps more important, because these criteria are not actually recommended for use in clinical practice; they were derived to facilitate studies of the disease. We did not rely solely on the College's criteria and accepted a rheumatologist's diagnosis of RA, recognizing that this would include patients who might not meet criteria; on the other hand, it provides a more realistic
Shmerling RH, Delbanco TL. The Utility of the Rheumatoid Factor-Reply. Arch Intern Med. 1993;153(16):1938. doi:10.1001/archinte.1993.00410160111014
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