The MBL concentration that def ines MBL def iciency is debated. Some define deficiency as a serum concentration , 500 ng/mL. 24, 31, 35, 36 Others def ine it as #100 ng/mL, and still others define severe deficiency as #50 ng/mL and partial deficiency as .50 ng/mL but ,1000 ng/mL. 9, 10, 21, 25, 31, [37] [38] [39] [40] The normal value reported by the manufacturer of the assay is 1135 ng/mL with a range of 103-3308 ng/mL (R&D Systems). Because of these uncertainties, we defined MBL deficiency in four ways, ie, #50 ng/mL, #100 ng/mL, #500 ng/mL, and .50 but #1000 ng/mL.