SIR, In the report by Helin et al in the Annals' the authors suggest that rheumatoid factor (RF) protects against nephropathy in patients with systemic lupus erythematosus (SLE). We have reviewed our series of 78 patients with SLE fulfilling the criteria of the above report for evaluating nephropathy and assaying RF. The Waaler-Rose sensitised sheep cell agglutination test was used to measure RF, with titres equal or greater than 1/64 considered positive. Both groups with and without renal disease were comparable for age and sex. A renal biopsy was performed in 38 out of 40 patients with nephropathy...