[Decrease of the 3rd fraction of serum complement. Study in a hospital population of 13000 patients].

Patients with serum concentrations of C3 lower than 0.40 g/l among 13 000 patients in a general hospital seen over an 18 months period were studied. 95 cases were eligible for study. Diffuse and severe liver disease accounts for 50% of cases. Immunologic diseases represent little more than 10% of cases. The other common causes are severe infections and nutritional deficiencies. Besides the immunological diseases, low C3 serum concentration represents a poor prognosis factor since 55% of patients died during hospitalization.