Background and Objectives The aim was to investigate the diagnostic and prognostic impact of the conventionally used autoantibodies (IgG) anti-CCP and IgM rheumatoid factor (RF) as well as IgA and IgG RF in the first ever collected cohort of Sudanese rheumatoid arthritis (RA) patients.
Materials and Methods 264 consecutive RA patients (87% females) diagnosed according to the 1987 ACR criteria attending two rheumatology centres in Khartoum between December 2008 and September 2010 were included, together with 168 healthy Sudanese blood donor controls. Autoantibody levels were investigated in Uppsala, and RF specificity levels aligned to the anti-CCP specificity (97.6%).
Results Anti-CCP was elevated in 52% (131/252) of the patients, a figure not different from what has been found in Sweden (57%, Rönnelid ARD 2005; p = 0.2). Among the Sudanese RA patient, 57.2%, 51% and 49.8% had IgA, IgM and IgG RF, respectively. The areas under the Receiver Operator Characteristics (ROC) curves were 0.94 for anti-CCP, and 0.95, 0.82 and 0.85 for IgA, IgG and IgM RF, respectively.
IgG RF was associated with young age (p = 0.0005) and lower age of disease onset (p < 0.0001), as well as with higher total number of affected joints (p = 0.03). Hand deformities like swan neck deformity (p = 0.0001) and boutonnière deformity (p = 0.02) were also primarily associated with IgG RF. Association with the other investigated autoantibodies were weaker or absent. The prognostic impact of IgG RF was not secondarily dependent on anti-CCP, as the correlation between anti-CCP was stronger for IgM RF (r = 0.49) and IgA RF (r = 0.31) than for IgG RF (r = 0.23).
Conclusions The occurrence of anti-CCP in Sudanese RA patients does not differ from Sweden. In contrary to what has been found in Caucasian RA populations, IgA RF is a diagnostically more sensitive marker than anti-CCP IgG RF is the strongest marker for bad prognosis, and associated with early disease onset.