An approach to ascertain probands with a non-traditional risk factor for carotid atherosclerosis

In our previous studies of the determinants of carotid plaque area (CPA), w e used a linear multiple regression model, which permitted us to control fo r the presence of known risk factors in order to reveal the contribution of putative new risk factors. We recognized that this approach could identify patients whose observed CPA was excessive when considering traditional ris k factors. Subjects whose observed CPA markedly exceeded the expected CPA w ere easily identified because of their deviation from the regression line t hat was derived using all members of the study sample. We classified such s ubjects as having 'unexplained atherosclerosis' relative to the overall stu dy sample when traditional risk factors were included as independent variab les. We then examined the plasma homocyst(e)ine concentration in members of the subgroup with 'unexplained atherosclerosis'. We found a significantly higher mean plasma concentration of homocyst(e)ine in the subgroup with 'un explained atherosclerosis', compared to rest of the study sample (20.4 +/- 4.3 vs. 13.2 +/- 3.2 mu mol/l, P < 0.005). We also found that significantly more subjects with 'unexplained atherosclerosis' had plasma homocyst(e)ine concentrations in excess of 14 mu mol/l compared to the rest of the study sample (52 vs. 33%, P < 0.002). We thus propose that systematic identificat ion of subjects with 'unexplained atherosclerosis' relative to the rest of a well-characterized study sample might be a useful approach to identify su bjects in whom there are newer, non-traditional determinants of predisposit ion to atherosclerosis. (C) 1999 Elsevier Science Ireland Ltd. All rights r eserved.