Hemolytic assay for the measurement of functional human mannose-binding lectin: a modification to avoid interference from classical pathway activation.

Diagnostic assays for measurement of functional mannose-binding lectin (MBL) in serum are widely performed as part of immune status assessment. Classical pathway mediated complement activity can interfere in these functional MBL assays. Here we describe classical pathway interference incidentally occurring in a previously described hemolytic MBL assay and the modification of this assay to prevent this artifact by addition of anti-C1q antibodies. Classical pathway interference in functional MBL assays can and should be inhibited to prevent that MBL deficiency is overlooked and patients are misdiagnosed.