Mannose-binding lectin: comparison of two assays for the quantification of MBL in the serum of pediatric patients.

Individuals with mannose-binding lectin (MBL)-deficiency are at an increased risk from infections with mannose-bearing microorganisms. We have investigated two quantitative research assays for measuring MBL protein in serum for routine diagnosis. The evaluation of 817 serum samples with a nephelometric assay revealed two deficiencies, a number far below the postulated 5-10% of the population. Reevaluation of 102 serum samples with an MBL-ELISA detected low levels in 27 cases (26.4%) and clear deficiencies in 21 samples (20.4%). In our hands, the MBL-ELISA permitted the detection of decreased levels of MBL in serum, as occurs in individuals with homozygous or heterozygous MBL gene mutations; in contrast, the nephelometric assay appeared to be unsuitable for the detection of MBL deficiencies. We support the routine measurement of MBL in serum, especially in children with frequent infections.