Screening with total cholesterol: determining sensitivity and specificity of the National Cholesterol Education Program's guidelines from a population survey.

The objective of the study was to determine the sensitivity and specificity of the National Cholesterol Education Program (NCEP) guidelines in identifying at-risk individuals for hypercholesterolemia, using population-based data from the Manitoba Heart Health Survey (MHHS). The MHHS surveyed a representative sample of adult residents of the province of Manitoba, Canada, aged 18-74 (n = 2792), 2212 of whom underwent complete lipoprotein analyses: total cholesterol (TC), high-density (HDL) and low-density (LDL) lipoprotein cholesterol, and triglycerides (TG) after overnight fasting. Following NCEP criteria for risk categories, 618 individuals could be considered as "at risk" based on their HDL and/or LDL levels. However, if the NCEP algorithms were followed, i.e. initial screen for TC only, and determination of HDL and LDL for selected individuals with borderline and high TC, only 438 of the total "at risk" individuals would have been identified (sensitivity = 71%). 1203 of 1594 individuals with acceptable HDL and LDL levels were not considered "at risk" on screening (specificity = 76%). If "at risk" status was determined solely on LDL criteria, the NCEP guidelines result in a higher sensitivity (94%) and comparable specificity (76%). However, when only HDL criteria were used, the sensitivity and specificity declined to 38% and 63% respectively. Compared to a simulated screening study based on the Lipid Research Clinic data reported by Bush and Riedel (1991) the estimates of sensitivity from the MHHS were high. Current NCEP guidelines appear to balance optimally the sensitivity and specificity for selecting individuals based on TC levels for further complete lipoprotein analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Health care seeking behavior following a health survey: impact on prevalence estimates of chronic diseases.

This article addresses the time sequence between a population health survey and subsequent health care use and how this changes the incidence estimates of selected chronic diseases. A cardiovascular survey of a representative sample of the adult population of Manitoba, Canada was linked with the health insurance claims database. Of the 2792 subjects in the survey, 98% were linked successfully, using an encrypted personal health insurance number. Five years of physician claims data for the survey participants were reviewed including 18 months prior to and 42 months following the survey. Survey participants started seeking confirmation of possible hypertension as soon as they received blood pressure information at the interview. Confirmation of diabetes and elevated cholesterol were not completed until 3-4 months after participants had received the laboratory test results. As many as 4.6 times more new cases of hypertension per month, 5.1 times more cases of elevated cholesterol, and 3.3 times more cases of diabetes were diagnosed following the survey. Surveys designed to determine the prevalence of specific chronic diseases generate new cases within a short time afterwards, thus affecting the original prevalence estimates. The process of assessing the burden of disease in a population is dynamic rather than static, and comparisons across populations need to take into account the frequency and recency of past surveys.

Comparison of survey and physician claims data for detecting hypertension.

Using linked data from the Manitoba (Canada) Heart Health Survey (MHHS) and physician service claims files we assessed the degree to which self-reported hypertension and clinically measured hypetension agreed with physician claims hypertension, and examined the likely sources of disagreement. The overall agreement between survey and claims data for hypertension detection was moderate to high: 82% (kappa = 0.56) for self-reported and physician claims hypertension, and 85% (kappa = 0.60) for clinically measured and physician claims hypertension. In the comparison between self-report and physician claims, those who were classified as obese, diabetic, or a homemaker were significantly more likely to have a hypertension measure not confirmed by the other. Disagreement between clinically measured and physician claims was also more common among the obese and homemakers, as well as those on medication for heart diseases, elevated cholesterol levels (LDL), and 35 years of age and older. The high overall level of agreement among these three measures suggest that each may be used with confidence as an indication of hypertension; however, the agreement appears lower among individuals presenting a more complicated clinical profile.

Vapor emissions resulting from Nd:YAG laser interaction with tooth structure.

UNLABELLED: The Neodymium:yttrium aluminum garnet (Nd:YAG) dental laser has been cleared by the United States Food and Drug Administration (FDA) for marketing in intraoral soft tissue treatment. The efficacy and safety of the Nd:YAG laser in the treatment of hard dental tissue as well as the effects of dental irradiation on the pulp and periodontium have been investigated. Odors resulting from laser irradiation have been reported, but the nature and toxicity of associated decomposition vapors is unknown and the health consequences of their inhalation have not yet been studied. OBJECTIVES: The purpose of this in vitro study was to identify vapors emitted during interaction of the Nd:YAG laser with carious human enamel and dentin and sound enamel and dentin coated with organic ink. METHODS: Vapor emissions were collected from prepared sections of extracted human teeth receiving laser irradiation of 100 mJ and 10 Hz for a duration of 1, 10, or 60 s. Emissions were collected by means of charcoal absorption tubes, and subsequently analyzed using a Gas Chromatograph equipped with Mass Selective (GC/MS) and Flame Ionization Detectors to identify the chemical constituents of the vapors. RESULTS: No compounds were identified in Nd:YAG laser-treated caries, enamel and dentin. No volatile vapors were identified from samples of tooth materials exposed to the laser for 1 or 10 s. Camphor was positively identified in the test sample which consisted of India ink-coated dentin and the reference sample of India ink-coated glass beads, both exposed to the laser for 60 s. 2,5-norbornadiene was tentatively identified in these samples. The Threshold Limit Value (TLV) of camphor is 2 ppm with a Lethal Dose Level (LDLo) of 50 mg/kg (human oral), while the TLV and LDLo of 2,5-norbornadiene is unknown. SIGNIFICANCE: Occupational and public health safety measures are discussed in this article. Further research is needed to quantify the compounds produced and to determine their toxicity to patients and to dental care providers.

The Manitoba Nutrition Survey: fat consumption data.

A nutrition survey was conducted as part of a larger cardiovascular risk study undertaken by the Manitoba Heart Health Project. A representative group of Manitobans participated in the study, 68% of whom reported their food intake using a food frequency questionnaire. After verifying and merging data from the nutrition and risk factor questionnaires used in the survey, 2,115 were used in data analysis. Results are reported by gender for three age groups. The proportion of food energy derived from total fat varied between 35.3% for senior females and 40.2% for young males. Food of seniors contained a lower proportion of energy from fat than that of either of the two younger age groups. In all three age groups, men consumed diets with a higher proportion of fat than did women. People in regional centres and rural areas obtained higher proportions of energy from fat than did people in Winnipeg. Fat intake from butter, margarine or spreads eaten with bread and potatoes was high compared to the intake from other foods.

Enhancement of rural community committee capacity for heart health promotion in Manitoba.

The province of Manitoba is 'rural' by nature, although 70% of its one million people reside within two large urban centres. The Manitoba Heart Health Project (MHHP) province-wide survey (1989) showed that cardiovascular disease (CVD) risk factors were highest and heart health-related knowledge was lowest in the rural population. Working with rural communities, the MHHP Demonstration Project (1992-95) carried out rural heart health promotion using a rural community committee-driven approach with appropriate training, limited resources and at low cost.

Energy-selective filtration of dental x-ray beams.

Samarium is known for its ability to filter simultaneously low- and high-energy x-ray photons from an x-ray beam that are not useful in producing a diagnostic radiograph. This study was undertaken to determine the optimum thickness of samarium required to minimize patient exposure and exposure time. The results indicate that use of a filter thickness of 0.16 mm. minimized patient radiation exposure and permitted the use of an exposure time sufficiently short to minimize motion unsharpness. The incorporation of a 0.16 mm. samarium filter in the x-ray beam reduced exposure by about 40 percent as compared to a 2.5 mm. aluminum filter; the exposure time must be increased approximately twice to obtain optical densities equivalent to those produced with aluminum filtration.

Is noncentral obesity metabolically benign? Implications for prevention from a population survey.

OBJECTIVE: To determine if individuals who are overall obese but have low waist-to-hip ratios have unfavorable lipid profiles, blood pressures, and glucose statuses. DESIGN: Cross-sectional study. SETTING: The Manitoba Heart Health Survey surveyed a representative sample of residents of the Canadian province of Manitoba. PARTICIPANTS: --A total of 2,792 adults aged 18 to 74 years were interviewed, 2,339 of whom underwent clinical examinations. MAIN OUTCOME MEASURES: Blood pressure, fasting plasma glucose, total cholesterol, triglycerides, high-density lipoprotein, and low-density lipoprotein measurements were compared across categories of body mass index (BMI) and waist-to-hip ratio (WHR). MAIN RESULTS: Manitobans with noncentral obesity tend to occupy positions between those of the nonobese and the centrally obese in terms of the effect on blood pressure, plasma lipids, and glucose. In multiple linear regression models involving age, BMI, and WHR as independent variables and one of the metabolic variables as dependent variables, both BMI and WHR are significant independent predictors of most metabolic variables. Where both are significant, BMI tends to be the stronger predictor, with a larger standardized regression coefficient. CONCLUSIONS: Noncentral obesity is not metabolically benign; BMI as an overall measure of obesity is as important as, and sometimes more important than, WHR in predicting metabolic effects. The recognition of the epidemiological significance of the WHR as a centrality measure of obesity should not divert attention from the metabolic risk status of noncentrally obese individuals who require continued health education to reduce weight.

A circuit modification that improves mammographic phototimer performance.

The typical mammographic phototimer does not track with breast thickness. For four common, relatively new mammographic units, phototimed density decreases markedly as breast thickness increases. This trend is attributed to three factors: beam hardening, film reciprocity law failure (RFL), and photosensor dark or leakage current. The contributions of these three factors were experimentally quantitated for the phototimer of a Senographé 500T mammography unit. For a phototimed 28-kVp nongrid technique, the density varied from 2.0 for a 2.5-cm-thick phantom to 0.3 for one 7.6 cm thick. Of the 1.7 difference in film density, 1.1 was attributed to beam hardening, 0.2 to RFL, and 0.4 to photomultiplier tube dark current. A circuit modification was installed in the phototimer that offsets the photomultiplier dark current and has a nonlinear response to compensate for beam hardening and RFL effects. The modified phototimer tracked to within +/- 0.06 density for a 28-kVp grid technique as phantom thickness was varied from 2.0 to 6.0 cm. Similar results were obtained for nongrid techniques.

Impact of atmospheric dispersion and transport of viral aerosols on the epidemiology of influenza.

Current theories of influenza viral epidemiology have not explained the persistence, seasonality, and explosive outbreaks of virus over large geographic areas. It is postulated in this paper that atmospheric dispersion and intercontinental scale transport of airborne aerosolized influenza virus may contribute to the spread, persistence, and ubiquity of the disease, the explosiveness of epidemics, and the prompt region-wide occurrence of outbreaks and that seasonal changes in circulation patterns and the dispersive character of the atmosphere may help to explain the regular annual cycle of influenza activity.

1979 diagnostic radiology services in the province of Manitoba.

This detailed study of a stable population compares the number and type of diagnostic radiology examinations, facilities, equipment, personnel and financial allocations for the years 1974 and 1979. The data have been obtained from $12.28 to $25.90. A computed tomography service began in 1977. The 1979 genetically significant radiation dose to the population is calculated to be 260 microgray. Continuing growth in computed tomography and diagnostic ultrasound with changing referrals for nuclear medicine are not yet ready for analysis.

Estimating the burden of disease. Comparing administrative data and self-reports.

OBJECTIVES: A cardiovascular health survey of a representative sample of the adult population of Manitoba, Canada was combined with the provincial health insurance claims database to determine the accuracy of survey questions in detecting cases of diabetes, hypertension, ischemic heart disease, stroke, and hypercholesterolemia. METHODS: Of 2,792 subjects in the survey, 97.7% were linked successfully using a scrambled personal health insurance number. Hospital and physician claims were extracted for these individuals for the 3-year period before the survey. RESULTS: The authors found no benefits to using restrictive criteria for entrance into the study (ie, requiring more than one diagnosis to define a case). Using additional years of data increased agreement between data sources. Kappa values indicated high levels of agreement between administrative data and self-reports for diabetes (0.72) and hypertension (0.59); kappa values were approximately 0.4 for the other conditions. Using administrative data as the "gold standard," specificity was generally very high, although cases with hypertension and hypercholesterolemia (diagnosed primarily by laboratory or physical measurement) were associated with a lower specificity than the other conditions. Sensitivity varied markedly and was lowest for "other heart disease" and "stroke". For diabetes and hypertension, inclusion criteria calling for more than one diagnosis reduced the accuracy of case identification, whereas increasing the number of years of data increased accuracy of identification. For diabetes and hypertension, self-reports were fairly accurate in detecting "true" past history of the illness based on physician diagnosis recorded on insurance claims. CONCLUSIONS: This study demonstrates the feasibility of linking a large health survey with administrative data and the validity of self-reports in estimating the prevalence of chronic diseases, especially diabetes and hypertension. A linked data set offers unusual opportunities for epidemiologic and health services research in a defined population.

Prevalence, control and awareness of high blood pressure among Canadian adults. Canadian Heart Health Surveys Research Group.

OBJECTIVE: To estimate the prevalence and distribution of elevated blood pressure (BP) among Canadian adults and to determine the level of control, treatment, awareness and prevalence of other risk factors among adults with high BP. DESIGN: Population-based cross-sectional surveys. SETTING: Nine Canadian provinces, from 1986 to 1990. PARTICIPANTS: A probability sample of 26,293 men and women aged 18 to 74 years was selected from the health insurance registers in each province. For 20,582 subjects, BP was measured at least twice. Nurses administered a standard questionnaire and recorded two BP measurements using a standardized technique. Two further BP readings, anthropometric measurements and a blood specimen for lipid analysis were obtained from those subjects who attended a clinic. OUTCOME MEASURES: Mean values of systolic and diastolic BP, prevalence of elevated BP using different criteria, and prevalence of smoking, elevated blood cholesterol, body mass index, physical activity and presence of diabetes by high BP status are reported. MAIN RESULTS: Sixteen percent of men and 13% of women had diastolic BP of 90 mm Hg or greater or were on treatment (or both). About 26% of these subjects were unaware of their hypertension, 42% were being treated and their condition controlled, 16% were treated and not controlled, and 16% were neither treated nor controlled. Use of non-pharmacologic treatment of high BP with or without medication was low (22%). Hypertensive subjects showed a higher prevalence of elevated total cholesterol, high body mass index, diabetes and sedentary lifestyle than normotensive subjects. Most people with elevated BP were in the 90 to 95 mm Hg range for diastolic pressure and 140 to 160 mm Hg range for systolic pressure. Prevalence of high isolated systolic BP sharply increased in men (40%) and women (49%) 65 to 74 years old. CONCLUSIONS: The relatively low level of control of elevated BP calls for population and individual strategies, stressing a non-pharmacologic approach and addressing isolated systolic hypertension in the elderly.

Where Manitoba children obtain their cigarettes.

People who start to smoke as children put themselves at greater risk of dying prematurely or being disabled by tobacco-induced disease. One solution is to restrict children's access to cigarettes, thereby reducing consumption of the product and, ultimately, damage to health. This study found that in 1985 the majority of Manitoba public school children 8 to 15 years of age who smoked "regularly" (defined as usually every day) obtained their cigarettes from stores. This source could be reduced, if not eliminated, were a federal regulation passed in 1908 enforced. Under Canada's Tobacco Restraint Act it is illegal for merchants to sell tobacco to anyone under the age of 16 years. By implementing this existing law, authorities would not only be keeping the profit from almost a million dollars in cigarette sales in Manitoba alone out of tobacco company coffers but also be having an impact on the leading cause of preventable premature death and disability in Canada.