Apolipoprotein B as a marker of familial hyperlipoproteinemia.

AIMS Families with 10-12-year-old schoolchildren were informed about and asked to participate in a study to identify children with hyperlipoproteinemia. We hypothesised that children and families with familial blood lipid abnormalities, specifically those with familial hypercholesterolemia (FH) and familial combined hyperlipidemia (FCHL), could be identified by the child's apolipoprotein B level exceeding the 95th percentile. METHODS Written information and consent was distributed to the families. Families whose child had an apoB concentration exceeding the 95th percentile were further examined. Children and parents were divided into normal, high and very high low density lipoprotein cholesterol (LDLC) groups. In adults a high LDLC level was defined as > 4.1-4.9, a very high as > 4.9 mmol/l, in children as > 3.4-4.1 and > 4.1 mmol/l, respectively. The triglyceride level was regarded as high when > 3.6 mmol/l. RESULTS Of 2,855 families, 2,186 agreed to participate. The 95th percentile apoB level was for boys 0.98 and girls 1.07 g/l. Of the 131 children with an apoB level above the 95th percentile, 109 families accepted further examinations. Of 109 hyperapoB children 23 were obese. Normal LDLC was found in 28 hyperapo B children of whom six parents had high/very high LDLC and one high triglyceride concentrations. A high LDLC level was found in 52 children of whom 23 parents had higy/very high LDLC and another five high LDLC and/or high triglyceride concentrations. A very high LDLC level was found in 29 children, in two of them due to hypothyroidism, 17 had a parent with high/very high LDLC and another two parents a high triglyceride concentration. Familial hypercholesterolemia, defined as a LDLC concentration above twice the normal one in the child and a very high level in a parent, was suspected in six families, five having a relative with premature CHD. The families with FCHL should be included in the 20 families with hyperapoB and a child with high-very high LDLC and a parent with very high LDLC or TG levels. CONCLUSION Of the 109 children examined due to the child's increased apoB concentration, about 20% were obese and 75% had an increased LDLC concentration. A familial occurrence of hyperlipoproteinemia was evident in about 50% of the families with an hyperapoB child. Six families probably suffer from familial hypercholesterolemia. The definite number of FCHL families could not be defined since extended pedigrees were not available. A high suspicion of FCHL was evident in 20 families. ApoB is an important marker of hyperlipoproteinemia of familial occurrence identifying families in need of primary CHD prevention.