The assessment of rheumatoid factor levels and hemogram parameters as predictors for rheumatologic disease

Many markers are used for clinical diagnosis in rheumatic diseases; rheumatoid factor (RF) is the most frequently used marker. However, RF is not specific to rheumatoid arthritis (RA). RF positivity is widely observed in patients with advanced age, infectious, autoimmune, and lymphoproliferative diseases. In this context, the objective of this study is to investigate the demographic characteristics, frequency of antinuclear antibody (ANA) and anti-cyclic citrullinated peptide (anti-CCP) positivity, hemogram parameters and distribution of the diagnoses in RF-positive patients followed at the rheumatology clinic.The population of this retrospective study consisted of patients above 18 years of age who were referred to have RF positivity by nephelometric method at Kahramanmaraş Necip Fazıl City Hospital Rheumatology Clinic between January 2020 and June 2022.The mean age of the 230 patients with a positive RF test result, 155 (76%) male and 55 (24%) female, was 52.7 ± 15.5 years. There were 81 (35.2%), 54 (23.5%), 73 (31.7%) and 22 (9.6%) patients with RF levels between 20 and 50 IU/mL, 50 and 100 IU/mL, 100 and 500 IU/mL, and above 500 IU/mL, respectively. There was no significant difference detected between the groups that were created based on the RF titers regarding demographic characteristics (P > 0.05). The rate of being diagnosed with any rheumatic disease was significantly lower in the group with RF levels between 20 and 50 IU/mL compared to other groups (P = 0.001). The distribution of rheumatic and non-rheumatic disease diagnoses according to RF levels did not reveal any significant difference between the groups (P = 0.369 and P = 0.147, respectively). RA was the most common (62.2%) rheumatic disease diagnosis among the patients included in the study. The leukocyte count was significantly higher in the group with RF levels above 500 IU/mL compared to the group with RF levels between 20 and 50 IU/mL (P = 0.024). There was no significant difference between the groups in other laboratory results, that is, hemogram, sedimentation, C-reactive protein, platelet, and lymphocyte/monocyte ratio (P > 0.05).The study findings indicate that RF positivity can be seen in the context of different rheumatological diseases; hence RF levels alone may not predict rheumatological disease. There was also no significant relationship between RF levels and ANA and anti-CCP positivity. The most common diagnosis in patients presenting with elevated RF levels was RA. Nevertheless, it should be noted that RF can be found asymptomatically in the general population.