Monthly intra-individual variation in lipoprotein(a) in 22 normal subjects over 12 months

OBJECTIVES: It is generally believe that lipoprotein(a) (Lp(a)) levels remain relatively constant in the same individual, but there is a paucity of data to substantiate this belief. This study was undertaken to determine the extent of intra-individual variation in Lp(a) over a 12-month period. DESIGN AND METHODS: Lp(a) was measured monthly in duplicate over a 12-month period in 11 females and 11 males who were healthy, free-living, normal subjects by the Incstar Immunoprecipitin method using a goat antibody which was monospecific for Lp(a). RESULTS: Some subjects showed considerable month-to-month variations which were not correlated with changes in other lipid parameters or with weight. Others showed fairly constant Lp(a) levels, with a few values which were quite different from the rest. This was not attributable to methodological factors; low and high controls gave mean (mg/L), SD and CV values of 181, 8.6, 4.7 and 431, 14, 3.3, respectively. The difference between the minimum and maximum values in the same individuals ranged from a low of 14 mg/L in one subject to a high of 229 mg/L in another over the one-year period. CONCLUSIONS: Lp(a) showed greater intra-individual variations in normal subjects than is commonly believed. It is therefore recommended that Lp(a) should be measured sequentially over a few weeks to arrive at a mean value for assessing risk of coronary heart disease.