Aaron R. Folsom

Short-term intraindividual variability in hemostasis factors the ARIC study

Recent epidemiologic studies found that there is a strong association of hemostatic factors with ischemic heart disease. The Atherosclerosis Risk in Communities (ARIC) Intraindividual Variability (IIV) Study was conducted to estimate the various components of variation in hemostasis factors measured in the ARIC Study and to estimate the measures of repeatability of these factors. A total of 39 subjects (16 men, 23 women) were studied. Each had blood collected three times, with a 1- to 2-week interval between each visit. The contributions of between-person variability, within-person (biologic) variability, and processing and assay variability were estimated. Then the reliability coefficient R was estimated as the proportion of total variance accounted for by between-person variance. The reliability coefficient can be interpreted as the correlation between measures made at repeat visits. Among the various analytes, the reliability coefficients were quite high for activated partial thromboplastin time and plasma factor VIII (R = 0.92, 0.86, respectively). Low repeatability was obtained for antithrombin III activity and protein C (R = 0.42, 0.56, respectively). The lack of repeatability for these variables derives mostly from the processing (field center and laboratory) variation. Other analytes--fibrinogen, plasma factor VII, and von Willebrand factor--were intermediate in repeatability. In comparing the analyte-specific high-level to low-level groups, no substantial difference of within-person plus method coefficient of variation between the two groups was found for any analyte except for factor VIII, whereas the corresponding variance components for most analytes were higher for the higher analyte level. Reliability coefficients from this ARIC IIV study are generally higher than those found in other studies, and this is related to the relative variations in populations studied and to the time between measurements.

Sex and race differences in short-term prognosis after acute coronary heart disease events: The Atherosclerosis Risk In Communities (ARIC) study

BACKGROUNDnCase fatality after myocardial infarction (MI) among patients admitted to the hospital may differ between men and women and blacks and whites. Furthermore, a different pattern of sex and race differences in case fatality may occur when coronary deaths outside the hospital are included in the analysis. The ARIC study provides community-based data to examine 28-day case fatality rates after coronary heart disease (CHD) events.nnnMETHOD AND RESULTSnSurveillance of out-of-hospital CHD deaths and hospitalized MI was conducted in 4 U.S. communities from 1987 to 1993. Hospital discharges and death certificates were sampled, medical records abstracted, and interviews conducted with witnesses of out-of-hospital deaths. MI and out-of-hospital death classifications followed a standard algorithm. Linkage of hospitalized MIs to fatality within 28 days ensured complete ascertainment of case fatality rate. Comorbidities and complications during hospital stay were compared to assess possible explanatory factors for differences in case fatality. Overall, age-adjusted 28-day case fatality (MI plus CHD) was higher in black men compared with white men (odds ratio 1.78, 95% confidence interval 1.4-2.2) and in black women compared with white women (odds ratio 1.5, 95% confidence interval 1. 2-2.0). Although men had higher overall case fatality rates than did women, this difference was not statistically significant. After a hospitalized MI, 28-day case fatality rate was not statistically significantly different between men compared with women or blacks compared with whites.nnnCONCLUSIONnRace and sex differences in case fatality after hospitalized MI were not evident in these data, although when out-of-hospital deaths were included, men and blacks were more likely than women and whites to die within 28 days of an acute cardiac event. A majority of deaths occurred before hospital admission, and additional study of possible reasons for these differences should be a priority.