The relation of sex, smoking status, birth rank, and parental age to beta2-glycoprotein I levels and phenotypes in a sample of Australian Caucasian adults.

The serum level of beta2-glycoprotein I has been measured in a sample of 532 healthy, unrelated Caucasians resident in Melbourne. The distribution of levels is bimodal but lacks complete separation of the two modes. Samples with levels below 14.0 mg/100 ml are considered to be type I, and those above this level to be type N. The present sample contains 42 subjects of the former phenotype and 490 of the latter. The phenotypes are distributed equally between males and females and between smokers and nonsmokers and are unrelated to age, birth rank, or parental age. The gene frequencies for the Melbourne sample are compared with those found in various European samples. The beta2-glycoprotein I level of type N males is higher than that of females, and smokers have a higher level than nonsmokers. The positive regression of level on age is significant when corrections are made for sex and smoking status. beta2-glycoprotein I level is highly correlated with pseudocholinesterase activity. The pattern of inheritance of phenotypes has been examined in 17 families with a total of 56 children. In all families, this pattern is consistent with the currently accepted mode of autosomal codominant transmission.