Notifying former patients of an infected health-care worker.
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Acquired Immunodeficiency Syndrome↗
Biomedical subjects
B Armstrong
Publications and source records attributed to B Armstrong.
Study design for exposure assessment in epidemiological studies.
We consider the implication, for study efficiency, of choice of method of exposure assessment in epidemiological studies, and in particular the optimal allocation of resources that should be devoted to improving the accuracy of exposure assessments. Useful for this purpose is a general result that the efficiency of a study based on approximate exposures relative to one based on exact exposures is equal to the square of the correlation between the true exposure and the approximate measurement in the study base (called the validity coefficient). This implies that to maximize study power, investment in increased precision is worthwhile up to the point at which proportional increase in total costs per subject exceed the proportional gain in the square of the validity coefficient. This result does not hold if exposure measurement error depends on disease status (is differential), or if important confounders are measured with error. 'Classical' exposure measurement error (uncorrelated with true exposure) or misclassification usually biases estimates of effect. Information from validity or reliability sub-studies can be used to correct this bias, but not substantially recover lost efficiency. There are several papers on the optimal allocation of resources to a validity sub-study.
Environmental Exposure↗
Erratum: Review of Particle Properties
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Journal Article↗
School-based health care for urban minority junior high school students.
OBJECTIVE: To describe the use of school-based health clinics by urban minority junior high school students. DESIGN: Review of demographic and utilization data collected by service providers during clinic visits. SETTINGS AND PARTICIPANTS: Health clinics in four junior high schools that enrolled predominantly Hispanic students who were residing in an economically disadvantaged, medically underserved New York (NY) school district. RESULTS: Of 5757 students who were enrolled in the schools, 5296 (92%) obtained parental consent to use the clinics, and 3723 (65%) used the clinics during the 1991-1992 academic year. Clinic users were 11 to 15 years old, 50% male and 50% female, 81% Hispanic and 14% black, and 29% sixth graders, 33% seventh graders, and 38% eighth graders. Clinic users made 16,340 clinic visits during the 1991-1992 academic year. Presenting complaints were mental health problems (32%), illness (14%), injury (12%), physical examination (5%), immunization (3%), follow-up (21%), and other (13%). Referral sources were clinic outreach (48%), self (44%), and school personnel (8%). Disposition of visits was on-site treatment (92%), referral to an affiliated hospital (5%), and referral elsewhere (3%). Compared with a nationwide group of high school-based clinics that served predominantly black adolescents, these clinics provided more mental health care (31% vs 21%), similar illness/injury care (32% vs 30%), and less preventive (10% vs 24%) and reproductive/contraceptive (7% vs 12%) care. CONCLUSIONS: Junior high school-based clinics can provide a wide range of primary and preventive health care services for large numbers of medically underserved youths. The provision of mental health services may fill a critical need among inner-city adolescents. Clinic outreach may be necessary to maximize utilization, especially among high-risk students.
Adolescent↗
Estimation of risk of developing bladder cancer among workers exposed to coal tar pitch volatiles in the primary aluminum industry.
To confirm the relationship between exposure to coal tar pitch volatiles and bladder cancer among primary aluminum production workers, we carried out a case-control study among blue-collar workers who had worked more than 1 year between 1950-1979 in a major plant using mostly the Soderberg process in the Province of Québec. Cases of bladder cancer (ICD code 188) diagnosed between 1970-1979 (n = 69) were mostly included in a previously reported study. To these were added cases diagnosed between 1980-1988 (n = 69). Each case was matched to three controls on date of birth, date of hiring, and length of service at the company. Smoking habits were assessed from the medical records at the company. Benzene-soluble matter (BSM) and benzo(a)pyrene (BaP) were used as indicators of environmental exposure to coal tar pitch volatiles in the workplace. The estimated risk for current smokers was 2.63 (95% C.I. 1.29-5.37). Estimates of risk by occupational exposure were adjusted for smoking. Men who had worked in the Soderberg potrooms were at higher risk of developing the disease, the risk increasing with the time spent in these departments. Similarly, a strong association between risk and cumulative exposure to BSM or to BaP was observed. The risks associated with cumulative exposure to BSM (mg/m3-years) and to BaP (microgram/m3-years) were described with mathematical models. Using a linear model (1 + bx) and lagging 10 years before the diagnosis, BaP cumulative exposure was a better indicator of risk than BSM cumulative exposure. The risk for each year of exposure to BaP at a concentration of 1 microgram/m3 increased by 1.7% (0.8%-3.2%). Using the same model for BSM, a worker exposed to the current threshold limit value of 0.2 mg/m3 for 40 years will sustain a risk of 2.22 (1.56-3.48). Comparison of risks according to different periods of diagnosis (1970-1979 vs. 1980-1988) did not reveal any significant temporal changes on risk estimates.
Air Pollutants, Occupational↗
Shock trauma Baltimore, USA.
Following attendance at a lecture by an anaesthetist who had spent time at the R. Adams Cowley shock trauma centre, and after seeing a documentary about Cowley's work on BBC TV, we began to investigate the possibility of spending time at the trauma centre as observers. In July 1993, we spent 2 weeks in Baltimore observing a system that has been tailored to meet the needs of multiply injured patients by utilising resources and the skills of all members of the multidisciplinary team.
Baltimore↗
Pulmonary retention of ceramic fibers in silicon carbide (SiC) workers.
The fibrous inorganic content of post-mortem lung material obtained from 15 men who worked in the primary silicon carbide (SiC) industry was evaluated. Five men had neither lung fibrosis nor lung cancer (NFNC), six had lung fibrosis (LF), and four had lung fibrosis and lung cancer (LFLC). The workers had 23 to 32 years of exposure. Mean duration of exposure was 23.4 (SD 6.9) years in the NFNC group, 28.8 (SD 5.5) in the LF, and 32.3 (SD 9.0) in the LFLC group. Concentrations of SiC ceramic fibers and other fibrous minerals and angular particles were determined by transmission electron microscopy and energy dispersive spectroscopy. The geometric mean and geometric standard deviation lung concentrations of SiC ceramic fibers < 5 microns were not statistically different for the three groups (Mann-Whitney, p > 0.1). Pulmonary retention of SiC fibers > or = 5 microns showed an excess in LF and LFLC cases combined versus NFNC that approached statistical significance (Mann-Whitney, p = 0.06). There was a somewhat greater difference for lung retention of ferruginous bodies between NFNC and either LF or LFLC cases (Mann-Whitney, p = 0.02). SiC fibers > or = 5 microns and angular particles containing Si and especially ferruginous bodies were found at higher concentrations in LF and LFLC than in NFNC cases.
Air Pollutants, Occupational↗
Sexual, assaultive, and suicidal behaviors among urban minority junior high school students.
OBJECTIVE: A greater understanding of minority adolescents' involvement in sex and violence is an essential precursor to the development of effective prevention programs targeted at inner-city youths. METHOD: To estimate the prevalence of involvement in sexual, assaultive, and suicidal behaviors and to quantify the relative importance of demographic, psychosocial, and behavioral risk factors for those behaviors, a survey was administered in the spring of 1992 to a sample of 3,738 predominantly Hispanic and African-American students attending four junior high schools in an economically disadvantaged, medically underserved New York City school district. The mean age of participants was 13.5 years; 73.7% were Dominican, 6.9% were other Hispanic, and 10.4% were black. RESULTS: Thirty-one percent of males and 7% of females reported involvement in sexual intercourse, 27% of males and 8% of females reported involvement in assaultive behavior and 10% of males and 19% of females reported suicide intentions/attempts. The primary risk factor for sexual intercourse was a belief that involvement in intercourse was common and acceptable among peers. The primary risk factor for assaultive behavior was adverse social circumstances. The primary risk factor for suicide intentions/attempts was symptoms of depression. The risk for involvement in each of the three investigated risk behaviors was substantially increased by involvement in the other two behaviors. CONCLUSIONS: These findings underscore the urgent need for comprehensive sex and violence prevention programs targeted at urban minority junior high school students and suggest factors that may identify students at highest risk.
Adolescent↗
Catheter interruption of atrioventricular conduction using radiofrequency energy in a patient with transposition of the great arteries.
Percutaneous catheter mapping and radiofrequency ablation of the AV node-His bundle system (with subsequent transvenous endocardial ventricular pacing) were performed on an 18-year-old woman with transposition of the great arteries and intact ventricular septum and chronic arrhythmias 15 years following a Mustard operation. Exclusion of the AV conduction tissue from the systemic venous circulation by the complex anatomy and the Mustard repair was circumvented by a retrograde approach across the aortic valve to the morphological right ventricle yielding access to the AV node-His bundle system.
Adolescent↗
The use of intraaortic balloon counterpulsation in acute myocardial infarction and high risk coronary angioplasty.
Patients with complex coronary arterial stenoses, decreased ejection fraction, or acute myocardial infarction are at increased risk during percutaneous coronary interventions. Intraaortic balloon counterpulsation (IABP) can provide benefit in such cases by several mechanisms. Myocardial perfusion is improved and left ventricular afterload is reduced by balloon counterpulsation. Patients with cardiogenic shock clearly benefit from balloon counterpulsation until revascularization can be performed. Recent studies have documented the utility of balloon counterpulsation in patients undergoing angioplasty as treatment for an acute myocardial infarction. Balloon counterpulsation is also an effective means to reduce ischemia and provide hemodynamic support during complex percutaneous coronary interventions. This review will summarize the benefits, indications, and complications of balloon counterpulsation during acute myocardial infarction and high-risk coronary angioplasty.
Angioplasty, Balloon, Coronary↗
The role of the perfusion balloon catheter after an initially unsuccessful coronary intervention.
Major dissection and acute closure following conventional percutaneous transluminal coronary angioplasty (PTCA) occur in 5%-10% of cases and lead to significant morbidity. Newer percutaneous modalities such as directional coronary atherectomy (DCA), excimer laser coronary angioplasty (ELCA), rotational ablation, and transluminal extraction atherectomy (TEC) can also be complicated by dissection and acute closure. Redilatation with conventional balloon catheters can reestablish patency of the artery or improve flow in a minority of cases. The perfusion balloon catheter (PBC) has several advantages over conventional balloon angioplasty in this situation. In approximately 70% of these cases, subsequent use of a PBC yields an acceptable clinical and angiographic result. The PBC permits rapid resolution of ischemia caused by acute closure or a flow-limiting dissection. New modifications of the PBC make it possible to position the catheter in nearly all segments of the coronary arterial tree including locations not accessible to other modalities, such as coronary stents or DCA, that are also used for salvage after a failed coronary intervention. Even if the PBC does not yield a definitive result, it allows rapid restoration of antegrade flow prior to coronary artery bypass grafting or coronary stent placement. Because of its ease of use, wide applicability, and efficacy, the PBC should be considered as the initial means of treatment in cases of major dissection or acute closure following any modality of percutaneous coronary revascularization.
Angioplasty, Balloon, Coronary↗
Client/server: where are we really?
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Computer Communication Networks↗
Sample size formulae for estimating the true arithmetic and geometric mean of lognormal exposure distributions.
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Humans↗
Cohort study of silicon carbide production workers.
Silicon carbide is produced by a chemical reaction at high temperature between free crystalline silica and petroleum coke. The process generates airborne fibers and fibrogenic dusts such as alpha-quartz and cristobalite, which are also potentially carcinogenic. The authors report that this is the first cohort study in this industry. The study was carried out among 585 Québec silicon carbide production workers who had worked at any time from 1950 to 1980. Follow-up was to December 31, 1989, and 167 deaths were observed. The standardized mortality ratio (SMR) for all causes of death was 1.05 (95% confidence interval (CI) 0.90-1.23); for nonmalignant respiratory diseases it was 2.03 (95% CI 1.21-3.22); and for lung cancer it was 1.69 (95% CI 1.09-2.52). Controlling for smoking status using a Cox regression analysis, the risk for nonmalignant respiratory diseases and for lung cancer increased with exposure to total dust; in the highest exposure category, rate ratios (RR) were 4.08 (95% CI 1.11-14.96) for nonmalignant respiratory diseases and 1.67 (95% CI 0.57-4.83) for lung cancer. Results were in the expected direction, but the power of the study was low, because of small sample size and use of cumulative total dust as the exposure variable, which may be a poor indicator of lung irritants and other potential carcinogens in this industry, notably silicon carbide ceramic fibers.
Adult↗
Association between exposure to pulsed electromagnetic fields and cancer in electric utility workers in Quebec, Canada, and France.
The authors report the association between exposure to pulsed electromagnetic fields (PEMFs) and cancer in a nested case-control study of electric utility workers in Quebec, Canada (follow-up, 1970-1988), and France (follow-up, 1978-1989), among whom 2,679 cases of cancer were identified. Exposures were assessed through a job-exposure matrix based on about 1,000 person-weeks of measurements from exposure meters worn by workers. Exposures were considerably higher in Quebec than in France. No association was found between PEMFs and cancers previously suspected of association with magnetic fields (leukemia, other hematopoietic cancers, brain cancer, or melanoma). However, there was a clear association between cumulative exposure to PEMFs and lung cancer, with odds ratios rising to 3.11 (95% confidence interval (CI) 1.60-6.04) in the highest exposure group (84 cases). This association with largely confined to Quebec, where there was a monotonic exposure-response relation with an odds ratio of 6.67 (95% CI 2.68-16.57) in the highest exposure group (32 cases). The association is substantial and was not explained by smoking or other occupational exposures. However, several factors limit the strength of the evidence for a causal relation: lack of precision in what the meters measured; little previous evidence for this association; and no elevated risk for lung cancer in the utility workers overall in comparison with the general population.
Case-Control Studies↗
Cancer risks associated with occupational exposure to magnetic fields among electric utility workers in Ontario and Quebec, Canada, and France: 1970-1989.
To determine whether occupational exposure to magnetic fields of 50-60 Hz was associated with cancer among electric utility workers, the authors used a case-control design nested within three cohorts of workers at electric utilities: Electricité de France--Gaz de France, 170,000 men; Ontario Hydro, 31,543 men; and Hydro-Québec, 21,749 men. During the observation period, 1970-1989, 4,151 new cases of cancer occurred. Each participant's cumulative exposure to magnetic fields was estimated based on measurements of current exposure of 2,066 workers performing tasks similar to those in the cohorts using personal dosimetry. Estimates were also made of past exposure based on knowledge of current loading, work practices, and usage. Workers who had more than the median cumulative exposure to magnetic fields (3.1 microtesla (microT)-years) had a higher risk for acute nonlymphoid leukemia (odds ratio (OR) = 2.41, 95% confidence interval (CI) 1.07-5.44). The same observation holds for acute myeloid leukemia (OR = 3.15, 95% CI 1.20-8.27). There was also an elevated risk for mean exposure above 0.2 microT (acute nonlymphoid leukemia, OR = 2.36, 95% CI 1.00-5.58; acute myeloid leukemia, OR = 2.25, 95% CI 0.79-6.46). However, there were no clear dose-response trends with increasing exposure and no consistency among the three utilities. Men whose cumulative exposure to magnetic fields was above the 90th percentile (15.7 microT-years) had an elevated risk for brain cancer (OR = 1.95, 95% CI 0.76-5.00) that was not statistically significant. No association with magnetic fields was observed for any of the other 29 types of cancer studied, including skin melanoma, male breast cancer, and prostate cancer. Controlling for potential confounding factors did not change the results.
Aged↗
Lung cancer mortality and polynuclear aromatic hydrocarbons: a case-cohort study of aluminum production workers in Arvida, Quebec, Canada.
The authors report the results of a case-cohort study of 338 lung cancer deaths in 1950-1988 and a random sample (sub-cohort) of 1,138 from among 16,297 men who had worked at least one year between 1950 and 1979 in manual jobs at a large aluminum production plant. In the past, certain workers were exposed to substantial quantities of coal tar pitch volatiles, a mixture known to include polynuclear (polycyclic) aromatic hydrocarbons, and thus suspected to be capable of causing lung cancer. After they controlled for the effects of smoking, the authors found that rate ratios rose with cumulative exposure to coal tar pitch volatiles measured as benzene-soluble material to 2.25 (95% confidence interval (CI) 1.50-3.38) at 10-19 mg/m3-years benzene-soluble matter, but did not rise further at higher exposures. The data are compatible with a linear relation with benzene-soluble matter (rate ratio (RR) = 1 + 0.031 mg/m3-years benzene-soluble matter). This model predicts a rate ratio of 1.25, and lifelong excess risk of 2.2%, after 40 years exposure at the current hygiene standard (0.2 mg/m3). A curved relation (RR = 1 + 0.098 mg/m3-years benzene-soluble matter 0.7) fitted somewhat better. Under this model, the predicted risks after this exposure are higher: 1.42 and 3.8%. The data are compatible with both additive and multiplicative models for the combined effect of smoking and coal tar pitch volatiles.
Adult↗
c-myc expression correlates with suppression of c-kit protooncogene expression in small cell lung cancer cell lines.
The mRNAs encoding the c-kit protooncogene tyrosine kinase receptor and its ligand, hemopoietic stem cell factor, are coexpressed in the majority of small cell lung cancer cell lines, suggesting that an autocrine growth loop may exist. Functional c-kit protein levels correspond well with mRNA levels in these cells. We have observed that those cell lines which express the c-kit gene also express either the L- and N-myc genes; those cell lines which express the c-myc gene do not express the c-kit gene. We have determined, by analyzing several small lung cancer cell lines transfected with a c-myc expression vector, that heterologous expression of c-myc correlates with a marked down-regulation of c-kit expression. Regulation of c-kit expression by the myc gene family may be partly responsible for the differing biological properties of cell lines and tumors which express N- and L-myc versus those that express c-myc.
Carcinoma, Small Cell↗