[1] Univ Pretoria, Fac Hlth Sci, Dept Immunol, Pretoria, South Africa
[2] Natl Hlth Lab Serv South Africa, Tshwane Acad Div, Pretoria, South Africa
[3] Univ Pretoria, Fac Hlth Sci, Dept Internal Med, Pretoria, South Africa
[4] Univ Pretoria, Fac Hlth Sci, Dept Internal Med, Div Rheumatol, Pretoria, South Africa