Laboratory examination of seronegative and seropositive rheumatoid arthritis.

In response to the continuing debate whether seronegative and seropositive rheumatoid arthritis (RA) are parts of the same disease spectrum or are distinct disorders, we performed a comparative analysis of some laboratory characteristics. The test group consisted of 125 seronegative RA(93 female, 32 male), with titers lower than 1/64 as defined by Rose-Waaler test. The control group consisted of 125 seropositive RA patients (93 female, 32 male), with titers of 1/64 or higher. Patients all belonged to the 2nd and 3rd functional classes (ARA), and were between 25-60 years of age. The duration of the disease was 1-27 years. Elevated average values of erythrosedimentation (ERS), C-reactive protein (PCR) and erythrocytes (Er) were found in seropositive patients, but they did not present statistically significant difference with regard to sero-status. Reduced values of hemoglobin (Hb) were found more frequently in seropositive patients (t = 2.26, p < 0.05), especially female seropositive patients (t = 4.38, p < 0.01), without correlation to disability and duration of the disease. Statistically significant difference was found in average values of fibrinogen in the seropositive subset (t = 2.10, p < 0.05), especially in female seropositive patients (t = 2.65, p < 0.01), and in average values of leukocytes (t = 1.37, p < 0.05) among male seropositive patients. Elevated immunoglobulin (IgM) values were more prominent in the seropositive subset (chi2 = 47.6, p < 0.01), especially among seropositive females (chi2 = 35.68, p < 0.01). Values of IgA and IgG did not present statistically significant difference with regard to sero-status. Levels of C3 and C4 components of the complement were reduced in seropositive tested subjects, without significant difference between sero-subsets. Increased values of gamma-globulin were confirmed with statistical significance (chi2 = 3.39, p < 0.05) in seropositive subjects, while alpha-2 globulin values were nearly equally distributed in both subsets.