[1] Uppsala Univ, Immunol Genet & Pathol, Uppsala, Sweden
[2] Al Neelain Univ, Fac Med Lab Sci, Khartoum, Sudan
[3] Karolinska Inst, Karolinska Univ Hosp, Div Rheumatol, Dept Med Solna, Stockholm, Sweden
[4] Uppsala Univ, Sect Clin Chem, Dept Med Sci, Uppsala, Sweden
[5] Lund Univ, Dept Expt Med Sci, Lund, Sweden
[6] Mil Hosp, Rheumatol Unit, Omdurman, Sudan
[7] Alribat Univ Hosp, Rheumatol Unit, Khartoum, Sudan