Erythrocyte sedimentation rate, C-reactive protein, or rheumatoid factor are normal at presentation in 35%-45% of patients with rheumatoid arthritis seen between 1980 and 2004: analyses from Finland and the United States.

OBJECTIVE: To analyze erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and rheumatoid factor (RF) tests in 2 databases of consecutive patients with rheumatoid arthritis (RA) over 25 years between 1980 and 2004, in Finland and the USA.
METHODS: Databases of 1892 patients of 7 rheumatologists in Jyväskylä, Finland, and 478 of one author in Nashville, TN, USA, seen in usual care, were reviewed for the first recorded ESR and CRP, and all RF tests.
RESULTS: Median ESR at presentation was 30 mm/h at both sites. Mean ESR was 36 mm/h in Jyväskylä and 35 mm/h in Nashville. ESR was < 28 mm/h in 45% and 47% of patients at the 2 sites, respectively. CRP was normal in 44% and 58%, and all RF tests were negative in 38% and 37%, respectively. Both ESR and CRP were normal in 33% and 42% of patients, and all 3 tests were normal in 15% and 14% of patients in whom they were assessed. All 3 tests were abnormal in only 28% in Jyväskylä and 23% in Nashville.
CONCLUSION: A majority of patients with RA seen between 1980 and 2004 had abnormal ESR, CRP, or RF. However, more than 37% of patients had ESR < 28 mm/h, normal CRP, or all negative RF tests. Similarities of laboratory test data at 2 sites on different continents with different duration of disease suggest generalizability of the findings. Normal ESR, CRP, and RF are seen in a substantial proportion of patients with RA at this time.