Screening for complement deficiencies in unselected patients with meningitis.

Two hundred and nine patients consecutively admitted to hospital with a tentative diagnosis of meningitis were screened for complement deficiency by measuring classical and alternative pathway serum haemolytic complement activity and the plasma concentration of C3d. Abnormal test results were followed up by quantitative immunochemical measurements of individual complement components. No patients with homozygous complement deficiency were found in our material. One patient with pneumococcal meningitis with probable heterozygous C2-deficiency was identified. Patients with purulent meningitis of various etiologies or meningococcal disease had significantly increased plasma C3d concentration at admission compared to patients with serous meningitis or without meningitis. Furthermore, increased plasma level of C3d at admission in patients with purulent meningitis or meningococcal disease was associated with an increased lethality. Our findings do not support the hypothesis that complement deficiency is commonly associated with sporadically occurring meningococcal disease or purulent meningitis.