Background Rheumatoid factor is known to be associated with smoking, malignancy, hepatitis B or C as well as many rheumatologic disorders not limited to rheumatoid arthritis. However, there have been no large-scale studies to prove these relationships. We conducted a retrospective study and presented the results at American college of rheumatology meeting in November 2011. This additional study was not planned at that time.
Objectives Age, smoking, malignancy, hepatitis B, and hepatitis C were confirmed as a risk factor and diabetes mellitus came up as a risk factor at the previous analysis. We performed analyses to describe these risk factors further including rheumatoid factor titers and hemoglobin A1c.
Methods St. Luke’s International Hospital Center for Preventive Medicine performs annual health examinations for more than 30,000 people each year, and rheumatoid factor is checked routinely during these examinations. The data in 2004 was obtained from the St. Luke’s Center for Preventive Medicine, including rheumatoid factor, past medical history (hypertension, hyperlipidemia, diabetes, ischemic heart disease, malignancy, hepatitis B or C), pulmonary function test and BMI. The people with known rheumatologic disorders were excluded. Additionally values of hemoglobin A1c and rheumatoid factor titer were obtained this time. These data were analyzed statistically.
Results A total of 31,207 patients were evaluated. The mean age was 49.1 and men consists of 50.7% of the group and women 49.3%. 6.8% had positive rheumatoid factor. As age increases, the rate of positive rheumatoid factor increases. However, there was no correlation between titer and age in multiple linear regression analysis. Multivariate logistic regression analysis with age and sex correction revealed smoking, malignancy hepatitis B and hepatitis C were risk factors for positive rheumatoid factor. Redefined DM (past medical history of diabetic mellitus and hemoglobin A1c greater than 6.5%) was no longer significant risk factor. Each odds ratio was as below. Smoking 1.08 (95% confident interval (CI): 1.02 - 1.15, P value <0.01), malignancy 1.28 (95%CI: 1.04 – 1.58, P value 0.02), hepatitis B 3.35 (95% CI: 2.33 – 4.80, P value <0.01), hepatitis C 2.82 (95% CI: 1.95 – 4.09, P value <0.01). Titer of rheumatoid factor with hepatitis B patient was significantly higher than that of patients with hepatitis C and that of patients with malignancy. (P value <0.01) Mean of hepatitis B patient was 106.2 U/mL, hepatitis C, 66.2 U/mL and malignancy 71.2 U/mL. There was no significant difference between hepatitis C and malignancy.
Conclusions The relationship between positive rheumatoid factor and conventionally estimated risk factors such as smoking, malignancy, hepatitis B, and hepatitis C is confirmed again. Diabetes Mellitus was no longer risk factor for positive rheumatoid factor among non-rheumatologic patients. The patients with hepatitis B showed statistically significantly higher rheumatoid factor titer. These factors are things to consider for patients with positive rheumatoid factor without clinical rheumatologic disorders.
Disclosure of Interest None Declared