Thrombocytopaenia in lupus as a marker of adverse outcome - seeking Ariadne's thread

Objective. To assess the role of thrombocytopaenia as an independent predictor of outcome in patients with systemic lupus erythematosus (SLE). Methods. This was a single-centre, retrospective, matched case-control study (1:2). Fifty consecutive Greek SLE patients were selected at random who had developed thrombocytopaenia during the disease course (cases) were compared with 100 SLE patients with no history of thrombocytopaenia, and matched for age, sex and disease duration (controls). Overall damage was assessed at the end of follow-up, using Systemic Lupus International Collaborating Clinics index. Total number of irreversible organ-damage events for both groups were recorded. Rates for specific outcomes and incidence-rate ratios (IRRs) for damage were estimated. Multivariate analysis estimating influential clinical and immunological factors for outcome, including thrombocytopaenia, was performed. Results. After 583 person-years of follow-up for cases and 1155 for controls, we found that thrombocytopaenic individuals have a higher risk for damage (IRR 1.96, 1.52-2.53) compared with their matched controls and this effect persists throughout the course of their disease. They also have a predilection to certain types of damage involving heart and kidneys. Among other significant factors associated with damage in multivariate analysis (disease activity, serositis, anti-cardiolipin antibodies, central nervous system involvement), thrombocytopaenia appears as the most influential. Conclusion. Thrombocytopaenia is a quantitive and qualitative marker of impending damage in SLE patients.