[Very high alpha-fetoprotein in a cirrhotic patient. Some comments].
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Adenocarcinoma↗
Biomedical subjects
J F Boivin
Publications and source records attributed to J F Boivin.
Risk factors for hepatitis C virus infection among street youths.
BACKGROUND: The relative contributions to risk of hepatitis C virus (HCV) infection resulting from unsafe sexual behaviours and exposures to blood (e.g., tattooing, body piercing and injection drug use) among youths at risk are not well known. We interviewed street youths about risk factors for HCV infection and documented their HCV antibody status. METHODS: From December 1995 to September 1996 we recruited 437 youths aged 14 to 25 years who met specific criteria for itinerancy. Data on sociodemographic characteristics and lifetime risk factors were obtained during a structured interview, and a venous blood sample was taken for HCV antibody testing. RESULTS: Many of the subjects reported behaviours that put them at risk for blood-borne diseases: 45.8% had injected drugs, 56.5% had at least 1 tattoo, and 78.3% had body piercing. The overall prevalence of HCV infection was 12.6% (95% confidence interval [CI] 9.7%-15.9%). In a multivariate logistic regression analysis, injecting drugs (adjusted odds ratio [OR] 28.4 [95% CI 6.6-121.4]), being over 18 years of age (adjusted OR 3.3 [95% CI 1.6-7.0]) and using crack cocaine (adjusted OR 2.3 [95% CI 1.0-5.3]) were independent risk factors for HCV infection. Having more than 1 tattoo (adjusted OR 1.8 [95% CI 0.95-3.6]) was marginally associated with HCV infection, and body piercing was not. INTERPRETATION: Drug injection was the factor most strongly associated with HCV infection among street youths. Given that injection drug users are the driving force of the HCV infection epidemic in Canada, increased intervention efforts to prevent initiation of drug injection are urgently needed to curb the epidemic.
Adolescent↗
Reduced food intake in response to CGP 71683A may be due to mechanisms other than NPY Y5 receptor blockade.
INTRODUCTION: The purpose of this study was to test the continuing validity of the hypothesis that neuropeptide Y (NPY) produced in the brain controls food intake through an interaction with the NPY Y(5) receptor subtype. METHODS: The hypothesis was tested using CGP 71683A a potent and highly selective non-peptide antagonist of the NPY Y(5) receptor which was administered into the right lateral ventricle of obese Zucker fa/fa rats. RESULTS: Intraventricular injection of 3.4 nmol/kg NPY increased food intake during a 2 h test period. Doses of CGP 71683A in excess of 15 nmol/kg (i.cv.) resulted in blockade of the increase in food intake produced by NPY. Repeated daily injection of CGP 71683A (30--300 nmol/kg, i.cv.) immediately before the dark phase produced a dose-dependent and slowly developing decrease in food intake. CGP 71683A has a low affinity for NPY Y(1), Y(2) and Y(4) receptors but a very high affinity for the NPY Y(5) receptor (Ki, 1.4 nM). Surprisingly, CGP 71683A had similarly high affinity for muscarinic receptors (Ki, 2.7 nM) and for the serotonin uptake recognition site (Ki, 6.2 nM) in rat brain. Anatomic analysis of the brain after treatment with CGP 71683A demonstrated an inflammatory response associated with the fall in food intake. CONCLUSIONS: While the fall in food intake in response to CGP 71683A may have a Y(5) component, interactions with other receptors or inflammatory mediators may also play a role. It is concluded that CGP 71683A is an imprecise tool for investigating the role of the NPY Y(5) receptor in the control of physiological processes including food intake. International Journal of Obesity (2001) 25, 84-94
Animals↗
Population preventable fraction of bicycle related head injuries.
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Accident Prevention↗
Functional outcome and satisfaction after photorefractive keratectomy. Part 2: survey of 690 patients.
PURPOSE: To document patient satisfaction and self-perceived quality of vision after bilateral photorefractive keratectomy (PRK). DESIGN: Noncomparative, interventional case series. PARTICIPANTS: Consecutive patients who underwent bilateral PRK from May 1994 through May 1997 by the 12 surgeons of four collaborating centers with a minimum of 4 months since the last surgery and up to 30 months since the first surgery. METHODS: A questionnaire with known psychometric properties was self-administered by the patients. MAIN OUTCOME MEASURES: Responses to individual questions and scale scores. RESULTS: A total of 929 questionnaires were sent, of which 690 were answered and returned (74.3% response rate). The preoperative spherical equivalent ranged from -0.38 diopters [D] to -27.75 D (mean, -5.32 D; standard deviation, 2.85 D). Although 91.8% of the patients were satisfied or very satisfied with their surgery, 96.3% considered that their main goal had been reached, and 95.7% would still choose to have surgery if they had it to do over. The degree of satisfaction was proportional to the postoperative uncorrected visual acuity in the best eye expressed in LogMAR (r = -0.18, P: = 0. 0001) and was negatively correlated with the importance of the corneal haze (r = -0.23, P = 0.0001). Daytime glare was reported to be greater than before surgery by 55.1% of patients. A decrease in night vision was reported by 31.7% of patients, and 31.1% of patients reported increased difficulty driving at night because of their vision. CONCLUSIONS: Overall satisfaction after PRK for low to severe myopia appears to be very good. Glare and night vision disturbance, particularly bothersome for night driving, seem to constitute significant secondary effects that deserve further investigation and should be kept in mind for future improvements in the technique.
Adolescent↗
Functional outcome and satisfaction after photorefractive keratectomy. Part 1: development and validation of a survey questionnaire.
OBJECTIVE: The aim of this study was to develop a valid, reliable, and easy-to-administer instrument to assess patient satisfaction and perceived outcome after bilateral excimer laser photorefractive keratectomy. DESIGN: Development and validation of a psychometric questionnaire. PARTICIPANTS: Consecutive patients who underwent bilateral excimer laser photorefractive keratectomy from May 1994 through May 1997 by 12 surgeons from four collaborating centers. To be eligible, a minimum of 4 months since the last surgery and a maximum of 30 months since the first surgery was required. METHODS: The new instrument was derived in part from the Prospective Evaluation of Radial Keratotomy (PERK) study 10-year psychometric questionnaire and the Visual Functional Index (VF-14), an index of functional impairment in patients with cataract. Questions were grouped in seven scales, each covering a specific aspect of quality of vision. These included global satisfaction, quality of uncorrected vision, quality of corrected vision, quality of night vision, glare, daytime driving, and night driving. MAIN OUTCOME MEASURES: Acceptability, reliability, validity, and interpretability of the instrument, as well as its ease of administration. RESULTS: The instrument scale structure was examined and scale scores were created. Item-discriminant validity ensured that questions belonged to their hypothesized scale, based on multitrait correlation analysis. The instrument was shown to be reliable by a high level of internal consistency, and all Cronbach's alpha coefficients were superior or equal to 0.83. Construct-related validity and interpretability were assessed based on correlations between scale scores and clinically recognized success criteria such as visual acuity and refraction. Respondent burden was shown to be minimal. Acceptability of the instrument was shown to be very good, with a participation rate of 74.3% (690 of 929 patients). The instrument is available in English and in French and the translation was shown to be reliable. CONCLUSIONS: The acceptability, reliability, and interpretability of the instrument, as well as its ease of administration, were shown to be adequate. This questionnaire appears clinically useful to document patient satisfaction after excimer laser photorefractive keratectomy.
Adolescent↗
Nested case-control study of the effects of non-steroidal anti-inflammatory drugs on breast cancer risk and stage.
We carried out a nested case-control study to measure the rate ratio (RR) for invasive female breast cancer in relation to non-steroidal anti-inflammatory drug (NSAID) use. The source population consisted of the female beneficiaries of the Saskatchewan Prescription Drug Plan from 1981 to 1995 with no history of cancer since 1970. Four controls/case, matched on age and sampling time, were randomly selected. Dispensing rates during successive time periods characterized NSAID exposure. RRs associated with exposure during each period were adjusted for exposure during the others. Confounding by other determinants was studied in analyses adjusted with data obtained by interviewing samples of subjects accrued from mid-1991 to mid-1995. We accrued 5882 cases and 23,517 controls. Increasing NSAID exposure 2-5 years preceding diagnosis was associated with a trend towards a decreasing RR (P-trend = 0.003); for the highest exposure level RR = 0.76, 95% confidence interval 0.63-0.92. This protective effect could not be attributed to confounding by other determinants. In analyses involving only the cases, NSAID exposure 2-5 and 6-10 years preceding diagnosis was associated with significantly reduced risks of presenting with a large tumour (> 5 cm diameter) or distant metastasis, but not regional lymph node metastasis. The use of NSAIDs may retard the growth of breast cancers and prevent distant metastasis.
Adult↗
Prevalence of HIV infection and risk behaviours among Montreal street youth.
We aim to estimate HIV prevalence and associated risk factors among street youth in Montreal, Canada. We conducted a one-year cross-sectional anonymous study in 1995. We recruited youth aged 13-25 years meeting specific criteria for itinerancy through the 20 major Montreal street youth agencies. Participation included a structured interview and provision of an oral specimen for HIV testing. Among the 909 subjects studied, 99.3% had been sexually active, 25.9% had exchanged sex for money, gifts, drugs, a place to sleep, or other things; 31.8% reported anal sex; and 36.4% reported having ever injected drugs. Overall, HIV prevalence was 1.9% (1.1% in girls and 2.2% in boys). Multivariate logistic regression showed that being over 20 years of age (adjusted odds ratio (AOR) 7.09), having injected drugs (AOR 4.48), having engaged in prostitution (AOR 3.32), and being born outside Canada (AOR 4.41) were all independently associated with HIV infection.
Adolescent↗
Hepatitis B virus infection among street youths in Montreal.
BACKGROUND: Street youths are at high risk for many health problems, including sexually transmitted diseases and bloodborne infections. The authors conducted a cross-sectional anonymous study from December 1995 to September 1996 involving street youths in Montreal to estimate the prevalence of risk behaviours for hepatitis B virus (HBV) infection and of markers of past and present HBV infection. METHODS: Participants were 437 youths aged 14 to 25 meeting specific criteria for itinerancy who were recruited in collaboration with the 20 major street youth agencies in Montreal. Sociodemographic and lifetime risk factor data were obtained during a structured interview, and a blood sample was taken to test for HBV markers (hepatitis B surface antigen and antibodies to the hepatitis B core antigen). Univariate analyses and multivariate logistic regressions were conducted. RESULTS: The mean age of the subjects was 19.5 years; 69.3% (303/437) were males. Many subjects had high-risk behaviours: 45.8% (200/437) had injected drugs, 24.5% (107/436) had engaged in prostitution, and 8.7% (38/437) reported having a sexual partner with a history of unspecified hepatitis. The prevalence rate for one or both HBV markers was 9.2% (40/434) (95% confidence interval [CI] 6.7%-12.3%). Multivariate logistic regression analysis showed that being over 18 years of age (adjusted odds ratio [OR] 4.5, 95% CI 1.8-11.7), having injected drugs (adjusted OR 3.5, 95% CI 1.5-8.3) and having had a sexual partner who had unspecified hepatitis (adjusted OR 3.2, 95% CI 1.3-7.5) were all associated with HBV infection. INTERPRETATION: Street youths are at high risk for HBV infection. Early and complete HBV vaccination among this vulnerable population is urgently needed.
Adolescent↗
Colorectal cancer prevention by non-steroidal anti-inflammatory drugs: effects of dosage and timing.
Epidemiological studies show that non-steroidal anti-inflammatory drugs (NSAIDs) reduce colorectal cancer incidence. We measured the rate ratio for colorectal adenocarcinoma according to dosage and the timing of exposure by means of a case-control study, nested in a non-concurrent cohort linkage study, using the population of beneficiaries of the Saskatchewan Prescription Drug Plan from 1981 to 1995 with no history of cancer since 1970 as the source population. Four controls per case, matched on age and gender and alive when the case was diagnosed, were randomly selected. Dispensing rates, calculated over successive time periods, characterized NSAID exposure. We accrued 3844 cases of colon cancer and 1971 cases of rectal cancer. For colon cancer a significant trend towards a decreasing rate ratio was associated with increasing exposure during the 6 months preceding diagnosis (P-trend = 0.002). For both cancers, significant trends were associated with exposure 11-15 years before diagnosis (colon: P-trend = 0.01; rectum: P-trend = 0.0001). At the highest exposure levels the rate ratio for colon cancer was 0.57 (95% confidence interval (CI) 0.36-0.89); for rectal cancer it was 0.26 (95% CI 0.11-0.61). No protection was associated with exposure during other periods. The timing of NSAID use must be considered in planning intervention trials to prevent colorectal cancer. There may be a 10-year delay before any preventive effect will appear.
Aged↗
Screening for prostate cancer: estimating the magnitude of overdetection.
BACKGROUND: No randomized controlled trial of prostate cancer screening has been reported and none is likely to be completed in the near future. In the absence of direct evidence, the decision to screen must therefore be based on estimates of benefits and risks. The main risk of screening is overdetection--the detection of cancer that, if left untreated, would not cause death. In this study the authors estimate the level of overdetection that might result from annual screening of men aged 50-70. METHODS: The annual rate of lethal screen-detectable cancer (detectable cancer that would prove fatal before age 85 if left untreated) was calculated from the observed prostate cancer mortality rate in Quebec; the annual rate of all cases of screen-detectable prostate cancer was calculated from 2 recent screening studies. RESULTS: The annual rate of lethal screen-detectable prostate cancer was estimated to be 1.3 per 1000 men. The annual rate of all cases of screen-detectable prostate cancer was estimated to be 8.0 per 1000 men. The estimated case-fatality rate among men up to 85 years of age was 16% (1.3/8.0) (sensitivity analysis 13% to 22%). INTERPRETATION: Of every 100 men with screen-detected prostate cancer, only 16 on average (13 to 22) could have their lives extended by surgery, since the prostate cancer would not cause death before age 85 in the remaining 84 (78 to 87).
Aged↗
Mortality among street youth.
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Adolescent↗
Selection of controls in database case-control studies: glucocorticoids and the risk of glaucoma.
In case-control studies conducted using computerized databases, controls are often selected as a random sample from the base population. This representative choice of controls is intended to guard against selection bias. We show, using data from a database case-control study, that such a definition of controls may also lead to selection bias under two conditions: (1) if the target disease has a prolonged asymptomatic clinical course with its detection depending on a specific physical examination and (2) if exposed patients have a higher likelihood of having the disease detected than unexposed patients. The extent of the bias that could result from the use of randomly selected controls was investigated in the context of a case-control study of the risk of ocular hypertension or glaucoma associated with the use of glucocorticoids, conducted using the Quebec universal health insurance computerized databases. This article also illustrates that a computerized database can be useful to empirically explore opportunities for bias.
Aged↗
Controlling confounding when studying large pharmacoepidemiologic databases: a case study of the two-stage sampling design.
Large drug databases have been the source of interesting developments for pharmacoepidemiologic research, because they provide relatively accurate drug exposure histories. An important limitation of these databases is the lack of information on potential confounders. One solution, developed more than a decade ago but not widely used, is "two-stage sampling," in which stage 1 is the collection of information on drug exposure and outcomes, and stage 2 is the collection of confounder data on a subset of the stage 1 sample. The balanced design, wherein an equal number of individuals is selected from each drug exposure/disease category, is usually the most efficient strategy by which to select the stage 2 sample. We illustrate the efficiency of the balanced design in two-stage sampling using data from a provincial health organization and a simulation. We also evaluate the relative importance of factors affecting the precision of the effect estimate of the exposure of interest.
Case-Control Studies↗
First treatment with inhaled corticosteroids and the prevention of admissions to hospital for asthma.
BACKGROUND: Early treatment with inhaled corticosteroids appears to improve clinical symptoms in asthma. Whether a first treatment initiated in the year following the recognition of asthma can prevent major outcomes such as admission to hospital has yet to be studied. METHODS: A case-control study nested within a cohort of 13,563 newly treated asthmatic subjects selected from the databases of Saskatchewan Health (1977-1993) was undertaken to investigate the effectiveness of a first treatment with inhaled corticosteroids in preventing admissions to hospital for asthma. Study subjects were aged between five and 44 years at cohort entry. First time users of inhaled corticosteroids were compared with first time users of theophylline for a maximum of 12 months of treatment. The two treatments under study were further classified into initial and subsequent therapy to minimize selection bias and confounding by indication. Odds ratios associated with hospital admissions for asthma were estimated using conditional logistic regression. Markers of asthma severity, as well as age and sex, were considered as potential confounders. RESULTS: Three hundred and three patients admitted to hospital with asthma were identified and 2636 matched controls were selected. subjects initially treated with regular inhaled corticosteroids were 40% less likely to be admitted to hospital for asthma than regular users of theophylline (odds ratio 0.6; 95% CI 0.4 to 1.0). The odds ratio decreased to 0.2 (95% CI 0.1 to 0.5) when inhaled corticosteroids and theophylline were given subsequently. CONCLUSION: The first regular treatment with inhaled corticosteroids initiated in the year following the recognition of asthma can reduce the risk of admission to hospital for asthma by up to 80% compared with regular treatment with theophylline. This is probably due, at least in part, to reducing the likelihood of a worsening in the severity of asthma.
Administration, Inhalation↗
Inhaled corticosteroids and the prevention of readmission to hospital for asthma.
Despite the proven efficacy of inhaled corticosteroids in reducing airway inflammation and their increasing use for the treatment of asthma since the mid 1980s, hospitalization for asthma has been increasing in frequency in several countries. Only few studies, reporting contradictory results, have investigated the role of inhaled corticosteroids in the prevention of hospitalizations for asthma. Using a cohort of 2,059 hospitalized asthmatic patients between 5 and 54 yr of age, we estimated the effectiveness of inhaled corticosteroids in preventing a readmission to hospital for asthma as a function of the duration of therapy. The cohort was selected from the databases of Saskatchewan Health from 1977 to 1993. The rate ratio (RR) of a readmission for asthma varied with duration of regular therapy with inhaled corticosteroids. During the first 15 d of regular therapy, users of inhaled corticosteroids were as likely as nonusers of these medications to be readmitted for asthma with a RR of 1.2 (95% CI: 0.8-1.8). Subjects treated regularly with inhaled corticosteroids for at least 16 d and as long as 6 mo were 40% less likely to be readmitted for asthma (RR = 0.6; 95% CI: 0.4-0.9), while after 6 mo of regular treatment the protective effect disappeared (RR = 1.3; 95% CI: 0.7-2.4). We conclude that regular therapy with inhaled corticosteroids can substantially reduce the risk of a readmission for asthma after only 15 d of use. Confounding by severity appears as the most likely explanation for the disappearance of the beneficial effect after 6 mo of regular therapy.
Administration, Inhalation↗
External comparisons from nested case-control designs.
The nested case-control design, used to sample within cohorts, is usually employed for internal comparisons. We propose to use this design for external comparisons. We present two probability-weighted estimators of the expected number of cases under a given exposure, based on external rates, for two versions of the nested case-control design. These estimators are used, along with their variance estimators, to form confidence intervals for standardized mortality ratios. The estimators are practically unbiased, whereas the naive estimator that treats the nested case-control sample as a random sample of the cohort is clearly biased. An estimator from the alternative Cox model-based approach is found to be substantially biased when applied in this context. Comparing the proposed estimators for nested case-control designs to a corresponding estimator for the case-cohort design, we found that the correlation between follow-up time and exposure time (that is, the amount of time under the exposure effect) has an impact on which type of design is more efficient for external comparisons. A small correlation favors the case-cohort design and a large correlation the nested case-control design. We examine empirical properties of these estimators through computer simulations, using a cohort study of the incidence of second cancer in 2,189 patients with Hodgkin's disease.
Bias↗
Risk of ocular hypertension or open-angle glaucoma in elderly patients on oral glucocorticoids.
BACKGROUND: Ocular hypertension and open-angle glaucoma are well-known side-effects of treatment with topical ophthalmic glucocorticoids. There is uncertainty about the risk of these disorders with oral glucocorticoid therapy. METHODS: Data from the Quebec universal health insurance programme for the elderly were used to identify 9793 patients with a new diagnosis of ocular hypertension or open-angle glaucoma, or on newly prescribed treatment for these disorders (cases). 38,325 controls were randomly selected from ophthalmology patients seen in the same month and year as the case (index date). Current use of oral glucocorticoids was defined as that within 14 days of the index date. All glucocorticoid doses were converted to the equivalent amount of hydrocortisone. The case-control analysis was done by conditional logistic regression and adjusted for age, sex, systemic hypertension, diabetes mellitus, ophthalmic glucocorticoids, glucocorticoid injections, and variables related to general health. FINDINGS: The mean ages of cases and controls were similar (74.9 [SD 6.3] vs 74.7 [6.4]). The adjusted odds ratio of ocular hypertension or open-angle glaucoma for current users of oral glucocorticoids compared with non-users was 1.41 (95% CI 1.22-1.63). There was a dose-related increase in the adjusted odds ratios for current users: 1.26 (1.01-1.56) for less than 40 mg per day of hydrocortisone, 1.37 (1.06-1.76) for patients on 40-79 mg per day, and 1.88 (1.40-2.53) for patients on 80 mg or more per day. The odds ratios also increased with the duration of treatment over the first 11 months of exposure. INTERPRETATION: The use of oral glucocorticoids increases the risk of ocular hypertension or open-angle glaucoma in elderly patients. In patients in this age-group who need long-term treatment with high doses of oral glucocorticoids, monitoring of intraocular pressure may be justified.
Administration, Oral↗