Predictive value of complement profiles and anti-dsDNA in systemic lupus erythematosus.

In a prospective study of 143 patients with systemic lupus erythematosus (SLE) the relation between clinical exacerbations, anti-dsDNA levels, and serum levels of complement components, C1q, C4, C3, C5, and C9 was investigated. In 33 out of these 143 patients a major clinical exacerbation of the disease developed. Evaluation of anti-dsDNA levels in relation to disease activity confirmed our earlier finding that anti-dsDNA levels rose before a major exacerbation and decreased after it. In the remaining 110 SLE patients a nearly constant anti-dsDNA level was seen, but none of these patients experienced a major exacerbation. In the 21 SLE patients who developed deterioration in renal function a decrease of C4 followed by decreases of C1q and C3 levels was seen first, starting about 25 to 20 weeks before the first signs of renal involvement. In the 12 SLE patients who developed an exacerbation without renal involvement an inconsistent profile of the complement components C4, C1q, and C3 was observed. C5 levels were hardly affected at all, while C9 levels were in general higher than normal during the exacerbation, irrespective of the type of exacerbation. These results show that, by following the complement and anti-dsDNA profiles, not only can exacerbations be predicted but also a pointer can be obtained about the pattern of disease well before the first clinical signs of an exacerbation appear.