Diagnostic accuracy for lupus and other systemic autoimmune diseases in the community setting

Most individuals with autoimmune and other immune disorders undergo initial evaluation in the community setting. Since misdiagnosis of systemic autoimmune diseases can have serious consequences, we evaluated community physicians' accuracy in diagnosing autoimmune diseases and the consequences of misdiagnosis.

We studied the patients referred to our Autoimmune Disease Center for 13 months (n = 476). We estimated the degree of agreement with the final diagnosis (kappa statistic) and the accuracy indexes (sensitivity, specificity, and predictive values) of the referring physicians' diagnoses.

We found a 49% agreement between the referring and final diagnoses (kappa = 0.36). Of 263 patients referred with a presumptive diagnosis of systemic lupus erythematosus (SLE), 125 received a diagnosis of other conditions (kappa = 0.34). Of those referred with SLE, 76 (29%) were seropositive for antinuclear antibodies but did not have autoimmune disease. The degree of agreement for referring rheumatologists (kappa = 0.55) was better than that for nonrheumatologists (kappa = 0.32). Stepwise logistic regression indicated that rheumatologists were 4 times more likely to make an accurate diagnosis of SLE than were nonrheumatologists (P<.003). Thirty-nine patients who were seropositive for antinuclear antibodies but had no autoimmune disease had been treated with corticosteroids at dosages as high as 60 mg/d.

Many patients with a positive antinuclear antibody test are incorrectly given a diagnosis of SLE and sometimes treated with toxic medications. The data support the importance of continuing medical education for community physicians in screening for autoimmune diseases and identifying patients who may benefit from early referral to a specialist.