Biomedical subjects

L E Chambless

Publications and source records attributed to L E Chambless.

At least 73 records · Page 4Linked to original sources

PubMed1996

A computer algorithm to impute interrupted heart rate data for the spectral analysis of heart rate variability--the ARIC study.

The shorter term beat-to-beat heart rate data collected from the general population are often interrupted by artifacts, and an arbitrary exclusion of such individuals from analysis may significantly reduce the sample size and/or introduce selection bias. A computer algorithm was developed to label as artifacts any data points outside the upper and lower limits generated by a 5-beat moving average +/- 25% (or set manually by an operator using a mouse) and to impute beat-to-beat heart rate throughout an artifact period to preserve the timing relationships of the adjacent, uncorrupted heart rate data. The algorithm applies Fast Fourier Transformation to the smoothed data to estimate low-frequency (LF; 0.025-0.15 Hz) and high-frequency (HF; 0.16-0.35 Hz) spectral powers and the HF/LF ratio as conventional indices of sympathetic, vagal, and vagal-sympathetic balance components, respectively. We applied this algorithm to resting, supine, 2-min beat-to-beat heart rate data collected in the population-based Atherosclerosis Risk in Communities study to assess the performance (success rate) of the algorithm (N = 526) and the inter-and intra-data-operator repeatability of using this computer algorithm (N = 108). Eighty-eight percent (88%) of the records could be smoothed by the computer-generated limits, an additional 4.8% by manually set limits, and 7.4% of the data could not be processed due to a large number of artifacts in the beginning or the end of the records. For the repeatability study, 108 records were selected at random, and two trained data operators applied this algorithm to the same records twice within a 6-month interval of each process (blinded to each other's results and their own prior results). The inter-data-operator reliability coefficients were 0.86, 0.92, and 0.90 for the HF, LF, and HF/LF components, respectively. The average intra-data-operator reliability coefficients were 0.99, 0.99, and 0.98 for the HF, LF, and HF/LF components, respectively. These results indicate that this computer algorithm is efficient and highly repeatable in processing short-term beat-to-beat heart rate data collected from the general population, given that the data operators are trained according to standardized protocol.

Algorithms↗

PubMed1996

Variability in B-mode ultrasound measurements in the atherosclerosis risk in communities (ARIC) study.

The Atherosclerosis Risk in Communities (ARIC) study is a multicenter, long-term epidemiologic study that uses B-mode ultrasound primarily to measure carotid arterial intima-media wall thickness. To assess the reliability of the measurement process of this application of B-mode technology to population-based research, 36 volunteers from four centers were scanned at three visits, 7-14 days apart. Estimates of the components of variation in the B-mode measurements of artery wall thickness from between-person, between-sonographer, within-sonographer, between-reader and within-reader variation are presented, along with estimates of the correlation R between measures made at repeat visits by different sonographers and read by different readers. The estimates of R for mean intima-media thickness are 0.69, 0.60, 0.54 and 0.66 for the carotid bifurcation, internal carotid, common carotid, and three-segment overall carotid mean, respectively. When these are adjusted to account for differences in between-person variance between the ancillary study and the main ARIC study, the estimated site-specific reliability coefficients appropriate to the ARIC study population are 0.77, 0.73 and 0.70 for mean carotid far-wall intima-media thickness at the carotid bifurcation and the internal and common carotid arteries.

Analysis of Variance↗

PubMed1996

Community surveillance of coronary heart disease in the Atherosclerosis Risk in Communities (ARIC) Study: methods and initial two years' experience.

The community surveillance component of the Atherosclerosis Risk in Communities (ARIC) Study is designed to estimate patterns and trends of coronary heart disease (CHD) incidence, case fatality, and mortality in four U.S. communities. Community surveillance involves ongoing review of death certificates and hospital discharge records to identify CHD events in community residents aged 35-74 years. Interviews with next of kin and questionnaires completed by physicians and medical examiners or coroners were used to collect information on deaths, and review and abstraction of hospital records were used to collect information on possible fatal and nonfatal myocardial infarctions (MIs). Events were classified using standardized criteria. The initial 2-years' experience with case ascertainment and availability of information needed for classification of events is described. Average annual age-adjusted attack rates of definite MI and CHD mortality rates for blacks in two communities and whites in the four communities are presented and compared with rates based on unvalidated hospital discharge data and vital statistics. Age-adjusted rates based on ARIC classification of definite MI were lower than those based on hospital discharge diagnosis code 410 (e.g., 5.60/1000 and 11.50/1000 among Forsyth County white men, respectively). Age-adjusted rates of definite fatal CHD based on ARIC classification were similarly lower than rates based on underlying cause of death code 410; for example, Jackson black men had rates of 2.82/1000 and 4.52/1000 for definite fatal CHD and UCOD 410-414 or 429.2, respectively.

Adult↗

PubMed1996

Differences between respondents and nonrespondents in a multicenter community-based study vary by gender ethnicity. The Atherosclerosis Risk in Communities (ARIC) Study Investigators.

This study provides data on differences between respondents and nonrespondents by gender and ethnicity in a multicenter community-based study that is rarely collected and that may be useful for estimating bias in prevalence estimates in other studies. Demographic, general health, and cardiovascular risk factors were examined in black and white respondents and nonrespondents to the Atherosclerosis Risk in Communities (ARIC) Study, a prospective study investigating cardiovascular risk factors in approximately 16,000 adults that was initiated in 1986 in four U.S. communities. In one of the communities (Jackson, MS) black participants were recruited exclusively; in another (Forsyth County, NC) 12% of the eligible sample were black, whereas the samples in Washington County, MD and the northwestern suburbs of Minneapolis, MN were almost all white. Demographic and health characteristics were collected during a home interview. Subjects who subsequently agreed to complete a clinical examination were defined as respondents, while eligible participants who only took part in the home interview were considered to be nonrespondents. Approximately 75% of age-eligible individuals (45-64 years) in each community completed the home interview. In three of the communities 86-88% of those who took part in the home interview also completed the clinic examination, whereas only 65% did so in Jackson. Among white participants, response rates were similar in men and women and between communities. Among black participants, the response rates were considerably lower, particularly in men. White male respondents reported a higher socioeconomic status, better general health and a lower prevalence of cardiovascular disease and associated risk factors than white male nonrespondents. The difference between white respondents and nonrespondents were greater for men than women despite similar response rates. Among black participants, respondent/nonrespondent difference were usually of smaller magnitude or absent, particularly in women. General health status and recent hospitalization rates were almost identical in black respondents and nonrespondents. Low response rates can bias estimates of prevalence in community-based studies although differences between respondents and nonrespondents tend to exaggerate real differences between respondents and the eligible population sampled. For example, among white males 25% of respondents and 44% of nonrespondents were current smokers, yet the estimated community prevalence of smoking was 31%. In conclusion, difference observed between respondents and nonrespondents were in the expected direction, but were greater for men than women and for whites than blacks.

Bias↗

PubMed1996

Population-based study of heart rate variability and prevalent myocardial infarction. The Atherosclerosis Risk in Communities Study.

Clinically based studies have indicated that patients who have suffered myocardial infarction (MI) exhibit lower heart rate variability (HRV). Such associations have not been reported at the population level. To investigate whether MI is related to lower HRV in the general population, the authors examined a stratified random sample of 2,243 men and women aged 45-64 years, of whom 260 had had MI and 1,983 were free of any coronary heart disease manifestations. All were part of the biracial cohort of the Atherosclerosis Risk in Communities study sampled from four United States communities. Resting, 2-minute supine heart rate data were analyzed using spectral analysis to estimate high-frequency (0.16-0.35 Hz) and low-frequency (0.025-0.15 Hz) spectral powers as conventional indices of HRV. The mean levels of high-frequency powers were 1.02 and 1.23 (beats/min)2 for MI and non-MI groups, respectively (P < .05), and the low-frequency means were 2.46 and 3.11 (beats/min)2 for MI and non-MI groups, respectively (P < .01). Age, race, and sex-adjusted odds ratios (95% confidence interval) of lower high-frequency and low-frequency powers contrasting MI to non-MI individuals were 1.52 (range, 1.09-2.10) and 1.54 (range, 1.12-2.10), respectively. After adjustment for use of beta-blocker medication, the odds ratios (95% confidence interval) were 1.26 (range, 0.88-1.81) and 1.22 (range, 0.87-1.69) for lower high-frequency and low-frequency powers, respectively. The findings from this first population-based study of prevalent MI and HRV provide support for an inverse association between MI and lower HRV. However, adjusting for beta-blocker use eliminates the statistical association. These findings confirm that impaired HRV is found in individuals with prevalent MI, even when drawn as a sample of community-dwelling individuals. This impaired HRV may contribute to the increased risk of subsequent cardiovascular events previously observed in survivors of acute MI. The cross-sectional data also suggest that use of beta-blockers diminishes the odds of lower HRV associated with MI.

Adrenergic beta-Antagonists↗

PubMed1996

Comparison of centralized versus "site-based" measurement of angiographic stenosis for eligibility in the asymptomatic carotid atherosclerosis study.

RATIONALE AND OBJECTIVES: The authors determine the reliability of centralized versus noncentralized (site-based) measurement of angiographic stenosis of patients enrolled into the multicenter, prospective, Asymptomatic Carotid Atherosclerosis Study by angiographic studies. METHODS: Percent agreements and correlations of 244 masked and prospectively interpreted angiograms were calculated for comparison of centralized and noncentralized readers measuring the percent carotid stenosis from the same angiographic studies. Univariate summary statistics for differences in percent stenoses were calculated for these readings. RESULTS: Agreement between readings were 88.5% and 91.8% with kappa statistics of 0.77 and 0.73 for > or = 60% and > or = 80% stenosis, respectively, for comparison of 33 centers to the designated central reader. Comparison between the designated central reader and a second central reader derived percent agreements of 85.0% and 86.5% with kappa statistics of 0.69 and 0.41 for > or = 60% and > or = 80% stenoses, respectively, for arteries selected from the original group. Hence, agreement was slightly better between the enrolling centers and the designated central reader than between the two central readers. CONCLUSIONS: Both centralized and noncentralized (site-based) methods of angiographic measurement of stenosis are equally reliable for large, prospective, masked, multicenter trials when quality control measures are instituted to ensure uniform application of eligibility criteria.

Angiography↗

PubMed1996

An approach for the use of Doppler ultrasound as a screening tool for hemodynamically significant stenosis (despite heterogeneity of Doppler performance). A multicenter experience. Asymptomatic Carotid Atherosclerosis Study Investigators.

BACKGROUND AND PURPOSE: The Asymptomatic Carotid Atherosclerosis Study (ACAS) Doppler validation study assessed the performance of individual Doppler machines across a spectrum of laboratories. We attempted to establish a threshold specific to individual machines to predict angiographically defined hemodynamic stenosis. The reliability of these Doppler ultrasound criteria was prospectively and independently evaluated among patients screened with ultrasound in the ACAS trial. METHODS: Regression techniques were used to establish the relationship between Doppler velocity and percent stenosis by angiography for 63 specific Doppler machines. This relationship was used to establish a Doppler threshold to provide a 90% positive predictive value (PPV) of a 60% stenosis by angiography. The sensitivity of each Doppler machine to detect a 60% stenosis (at the 90% PPV threshold) was estimated. The efficacy of these Doppler thresholds was then prospectively evaluated by calculating the PPV among ACAS participants eligible by ultrasound. RESULTS: Of the 63 machines, 13 (21%) had an excellent sensitivity (80%+) at 90% PPV. In 32 devices (51%) only a marginal sensitivity (50% to 80%) could be achieved. In 9 devices (14%) the sensitivity was poor (0% to 50%), and in 9 (14%) no threshold could be established. Despite the heterogeneity of Doppler performance, the standardization program worked as designed in the ACAS trial. Of 825 surgical patients, 399 were eligible by Doppler and 395 subsequently underwent angiography. Of these, 32 (8.1%; 95% confidence interval, 5.4% to 10.8%) did not have hemodynamically significant stenosis by arteriography, a proportion nonsignificantly lower than the planned 10% by the PPV. CONCLUSIONS: The performance of Doppler ultrasound was highly variable. This suggests that Doppler performance is likely overstated in the literature, but specific devices may perform satisfactorily to detect individuals with hemodynamically significant stenosis. Because performance differs substantially among devices, local investigators are strongly urged to maintain local standardization series. With such standardization, ultrasound performance is sufficient for admission to clinical trials and as the is sufficient for admission to clinical trials and as the basis for carotid surgery. However, without quality control many ultrasound machines are not adequate to accurately predict the degree of carotid stenosis and should not be the only test to decide whether surgery is warranted.

Angiography↗

PubMed1996

[Indications for endarterectomy in asymptomatic stenoses of the internal or common carotid artery--results of the North American ACAS Study].

OBJECTIVE: To determine the effect of endarterectomy on the primary prevention of ischemic stroke in patients with asymptomatic carotid artery stenosis. METHODS: In a prospective, randomized, multicenter trial 1659 patients with asymptomatic carotid stenosis of 60% or more were studied in two treatment arms (endarterectomy: n = 825; medical therapy: n = 834). Endpoints were: (1) ischemic stroke in the vascular territory of the study artery, (2) any perioperative stroke or any perioperative death. RESULTS: The Kaplan-Meier 5-year-risk estimation showed a relative risk reduction of 53% (confidence interval: 22%-72%) for patients in the surgical arm. The combined perioperative morbidity and mortality rate was 2.3%. CONCLUSION: Endarterectomy of asymptomatic carotid artery stenosis performed with a perioperative complication rate of less than 3% reduces the 5-year risk of ipsilateral stroke.

Adult↗

PubMed1995

Association of the waist-to-hip ratio is different with wine than with beer or hard liquor consumption. Atherosclerosis Risk in Communities Study Investigators.

Specific alcoholic beverage associations with the waist-to-hip ratio were characterized in 12,145 African-American and white men and women ages 45-64 years. Estimated waist-to-hip ratios of those consuming more than six nonwine alcohol drinks/week and more than six wine drinks/week (vs. nondrinkers) were 0.007 larger (p < 0.001) and 0.009 smaller (p < 0.05), respectively. In similar comparisons, the odds ratios for a large waist-to-hip ratio were 1.4 (95% confidence interval 1.1-1.7) for nonwine and 0.45 (95% confidence interval 0.21-0.95) for wine intake. The opposite direction in adjusted associations for wine and nonwine (mainly beer) drinking supports the popular concept of the "beer belly."

Adipose Tissue↗

PubMed1995

Age, race, and sex differences in autonomic cardiac function measured by spectral analysis of heart rate variability--the ARIC study. Atherosclerosis Risk in Communities.

To investigate the distribution of heart rate variability (HRV) spectral power in an unselected sample of the population, and to ascertain the population correlates of HRV, we examined 1,984 healthy persons, aged 45 to 64 years, randomly selected from the Atherosclerosis Risk in Communities (ARIC) study cohort. Resting, supine, 2-minute, beat-to-beat heart rate data were collected between 7 A.M. and 12 noon. The race- and sex-adjusted geometric means of low-frequency component (LF, 0.025 to 0.15 Hz) were 4.00 and 3.13 (beats/min)2; of high-frequency component (HF, 0.16 to 0.35 Hz), 1.65 and 1.21 (beats/min)2; and of the HF/LF ratio, 0.41 and 0.39, for 45-to-54 and 55-to-64 years age groups, respectively (test of mean difference by age, p < 0.01, p < 0.01, and p = 0.11 for LF, HF, and HF/LF ratio, respectively). Comparing black with white examinees, the age- and sex-adjusted geometric means of LF were 3.06 and 3.70 (beats/min)2; of HF, 1.66 and 1.36 (beats/min)2; of HF/LF, 0.54 and 0.37, respectively (test of mean difference by race, p < 0.01, p < 0.01, and p < 0.01). The age- and race-adjusted geometric means of LF for women and men were 3.12 and 4.10 (beats/min)2; of HF, 1.46 and 1.38 (beats/min)2; and of HF/LF, 0.47 and 0.34, respectively (test of mean difference, p < 0.01, p = 0.34, and p < 0.01). We conclude that HRV spectral indexes are associated with age, race, and sex. With increasing age, the parasympathetic and sympathetic spectral power components decrease.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗

PubMed1995

Effects of model misspecification in the estimation of variance components and intraclass correlation for paired data.

Paired data occur in many experimental situations. When one views the subjects as a random sample from some large population, it may seem reasonable to model the data according to the typical one-way random effects analysis of variance (ANOVA). It is then usually of interest to estimate variance components and intraclass correlation. These estimators can be biased if key assumptions are violated, leading to erroneous interpretations and conclusions. We focus upon assumptions about the equality or inequality of means and/or variances of the two measures on each subject. In the framework of the one-way random effects ANOVA model, and three generalizations of it, we document estimators obtained as solutions to the likelihood equations. We consider the potentially serious effects of mistaken assumptions. Our findings suggest that the most general model considered is most desirable if consistent and efficient estimation of the between-subject variance component and intraclass correlation is the main goal. We also briefly connect our exposition to the study of reliability or agreement.

Analysis of Variance↗

PubMed1995

Population awareness and control of hypertension and hypercholesterolemia. The Atherosclerosis Risk in Communities study.

BACKGROUND: A national program for hypertension detection and control was implemented in the 1970s, whereas a similar program for control of hypercholesterolemia has been implemented in recent years. We studied the levels of awareness, treatment, and control of these conditions in US population samples during a 3-year period (1987 to 1989). METHODS: The levels of awareness, treatment (by medication), and adequate control of hypertension (systolic blood pressure, > or = 140 mm Hg; diastolic blood pressure, > or = 90 mm Hg; or antihypertensive medication) and hypercholesterolemia (serum cholesterol level, > or = 6.21 mmol/L [> or = 240 mg/dL], or lipid-lowering medication) were studied among participants in the baseline examination of the Atherosclerosis Risk in Communities Study, including 15,739 individuals aged 45 to 64 years. RESULTS: Eighty-four percent of the hypertensive subjects and 42% of the hypercholesterolemic subjects were aware of their conditions. Overall, 50% of the hypertensive subjects and only 4% of the hypercholesterolemic subjects had their conditions both treated and controlled. Rates of hypertension prevalence, awareness, and control remained stable during the 3-year study period. Hypercholesterolemia prevalence decreased from 30% in 1987 to 25% in 1989; its awareness increased from 31% to 50% during the same period. Hypertensive women were more likely than hypertensive men to be aware and treated, whereas hypercholesterolemia awareness was higher in men than in women. Hypertension awareness was highest in black women, but black hypertensive subjects were less likely than whites to be treated and to have their hypertension controlled. Black hypercholesterolemic subjects were less likely to be either aware or treated. CONCLUSIONS: After the recent implementation of the National Cholesterol Education Program, the levels of awareness, treatment, and control of hypercholesterolemia are improving at a high rate, although they are still substantially lower than those for hypertension. Further improvement is necessary, particularly among certain population groups, such as blacks.

Age Distribution↗

PubMed1995

Fasting hyperinsulinemia and cardiovascular disease risk factors in nondiabetic adults: stronger associations in lean versus obese subjects. Atherosclerosis Risk in Communities Study Investigators.

The association between hyperinsulinemia and atherogenic risk factors has not been well studied in blacks and may be different for obese versus lean individuals. To investigate this possibility and to confirm the associations of hyperinsulinemia with cardiovascular disease risk factors in blacks and whites, we analyzed the joint associations of fasting serum insulin and obesity with risk factors in the Atherosclerosis Risk in Communities (ARIC) Study (1,293 black men, 4,797 white men, 2,033 black women, and 5,445 white women). Insulin values > or = 90th percentile (> or = 21 microU/mL) constituted hyperinsulinemia; body mass index (BMI) values > or = 27.3 kg/m2 for women and > or = 27.8 for men constituted obesity. Participants with hyperinsulinemia in all four race-sex groups had more atherogenic levels of most risk factors studied than those with normoinsulinemia. Among black men and women, mean levels of triglycerides, low-density lipoprotein cholesterol (LDL-C), apolipoprotein (apo) B, glucose, and fibrinogen (men only) were higher in hyperinsulinemic lean participants as compared with the normoinsulinemic obese group. Furthermore, most associations between insulin level and risk factors were stronger among lean versus obese subjects. For example, among lean black men, the difference in mean triglyceride concentration between those with hyperinsulinemia and those with normoinsulinemia was 147 - 99 = 48 mg/dL; among obese black men, the difference was 155 - 121 = 34 mg/dL (P < .05 for the interaction). Generally, similar negative interactions between BMI and insulin concentration were also observed among whites.(ABSTRACT TRUNCATED AT 250 WORDS)

Black People↗

PubMed1995

Correlates of body fat distribution. Variation across categories of race, sex, and body mass in the atherosclerosis risk in communities study. The Atherosclerosis Risk in communities (ARIC) Study Investigators.

Though central adiposity is a strong, independent risk factor for cardiovascular and all-cause mortality, relatively little is known about its determinants. To characterize the association of central adiposity with several of its possible determinants, while describing variability in these associations across sex, race, and level of body mass index, we conducted a cross-sectional survey of 15,800 white and African-American men and women ages 45 to 64 years participating in the Atherosclerosis Risk in Communities baseline survey, 1987 to 1989. After adjustment for other possible determinants, African Americans had markedly larger subscapular skinfold thickness and subscapular/triceps ratios than did whites, while whites had larger waist/hip ratios. Large, statistically significant variations in waist/hip ratio associations with age, percent of weight gained after age 25, smoking, and physical activity in the workplace existed across categories of sex, race, and body mass index. Based on our findings, we concluded that major variation exists in the waist/hip ratio and in its associations with its possible determinants across categories of race, sex and obesity.

Adipose Tissue↗

PubMed1995

Short- and long-term repeatability of fatty acid composition of human plasma phospholipids and cholesterol esters. The Atherosclerosis Risk in Communities (ARIC) Study Investigators.

We examined short-term and long-term repeatability (reliability) of the fatty acid (FA) composition of plasma phospholipids and cholesterol esters (CEs). For short-term reliability, fasting blood samples of 34 subjects were collected three times, 2 wk apart, and in 24 subjects duplicate samples were collected during each visit. For long-term reliability, two fasting samples were collected in 50 subjects approximately 3 y apart. In both phospholipids and CEs, short-term and long-term reliability coefficients were > 0.65 for the major plasma FAs (16:0, 18:0, 18:2n-6, and 20:4n-6), with the exception of 18:1n-9, but were generally lower for FAs that compose < 1% of total FAs. Reliability tended to be better for CEs than for phospholipids. Method variability was small (< 5% of total variability for most FAs), indicating that biological and dietary variability contribute most to total variability. Plasma FA measurement warrants consideration as a biochemical marker of diet in epidemiologic studies.

Cholesterol Esters↗

PubMed1995

Association of postprandial triglyceride and retinyl palmitate responses with asymptomatic carotid artery atherosclerosis in middle-aged men and women. The Atherosclerosis Risk in Communities (ARIC) Study.

Blood lipid alterations after a fatty meal may be atherogenic, but there is little information regarding their associations with disease independent of fasting lipids. Asymptomatic atherosclerosis cases (n = 229) and 373 control subjects free of atherosclerosis, as defined by carotid intima-media thickness on ultrasound images, were given a fatty meal with vitamin A, followed by 3.5- and 8-hour measurements of triglycerides (TGs), TG-rich lipoprotein TGs, apoproteinB48, and retinyl palmitate. Among white men and women but not among blacks, case status was associated with greater postprandial responses of TGs and TG-rich lipoprotein TGs, but only in nonobese persons (body mass index < 30 kg/m2). The associations were strong and significant after controlling for coronary risk factors (odds ratio, approximately 2.0) and fasting TGs (odds ratio, 1.5). Associations with other postprandial lipid measurements did not persist after controlling for fasting lipids. Elevated postprandial TGs appear to be an independent risk factor for carotid intimal thickening in nonobese whites. The lack of such a relation in obese subjects and the lipid profile they manifest suggest that postprandial TGs must be accompanied by accumulation of TG-rich lipoprotein remnants to be atherogenic.

Apolipoprotein B-48↗

PubMed1995

ARIC hemostasis study--IV. Intraindividual variability and reliability of hemostatic factors. The Atherosclerosis Risk in Communities (ARIC).

We have recently reported the short-term intraindividual variability of several coagulation factors and inhibitors included in the ARIC study (Chambless et al. Ann Epidemiol 1992; 2:723). In this paper, we reported the intraindividual variability results of additional hemostatic factors. Blood samples were collected for hemostatic assays three times at 1-2-week intervals from 39 subjects recruited from 4 ARIC field centers. The contributions of within-person, processing and assay (designated "method") and between-person variances to the total variance were estimated and from them the reliability coefficient, R, was computed as the proportion of total variance in the between-person component. The R value was high for beta-thromboglobulin and tissue-plasminogen activator: 0.83 and 0.81, respectively; and intermediate for D-dimer and plasminogen activator inhibitor-1: 0.73 and 0.72, respectively. Protein S (total and free) and platelet factor 4 had low repeatability (R < 0.50) derived mostly from "method" variability while low R value (0.03) for fibrinopeptide A was attributed to high "method" and "within-person" variability. Gender, age and the level of hemostatic factors did not influence the intraindividual variability.

Arteriosclerosis↗

PubMed1995

Reliability of body fat distribution measurements. The ARIC Study baseline cohort results. Atherosclerosis Risk in Communities Study.

OBJECTIVE: To estimate the reliability of skinfold and girth measurements, and ratios involving these measurements, commonly used in epidemiological and clinical studies as measures of body fat distribution. DESIGN: Repeated measurements of body fat distribution measures were scheduled on randomly selected participants at the baseline clinical examination of the ARIC Cohort Study, by the same or by different technicians. SETTING: Probability sample of 45-65 year old residents selected from four US communities. MEASUREMENTS: Subscapular and triceps skinfolds were taken twice using a Lange caliper on standardized right-side locations. Waist and hip girths were measured using an anthropometric tape applied at the level of umbilicus and of the maximal protrusion of the gluteal muscles, respectively. Repeated measurements were taken 1-2 h apart. RESULTS: Inter-technician measurements of triceps skinfolds, subscapular skinfolds, waist girth, hip girth, and waist/hip ratio each had high reliability (R > 0.91). The reliability coefficient for triceps/subscapular ratio (R = 0.81) was somewhat lower. For skinfold measures, intra-observer coefficient of variations are lower than the ones observed in previous studies, and inter-technician coefficient of variations are comparable. CONCLUSIONS: These results confirm previous findings which indicate that the reliability of girth measurements is greater than for skinfold measurements. As a consequence, the waist to hip ratio is less affected by measurement error than the skinfold ratio. Moreover, the expected gain in reliability from using the average of two skinfold measures, taken in succession, was not realized, indicating that when measurements are taken in rapid succession by the same technician, statistical independence between measures is questionable.

Analysis of Variance↗