PubMed Health⌕ Search

Biomedical subjects

David L Streiner

Publications and source records attributed to David L Streiner.

16 recordsLinked to original sources
PubMed2003

Stability of maternal preferences for pediatric health states in the perinatal period and 1 year later.

BACKGROUND: We have previously shown that parents of premature children provided relatively high valuation of their children's health state in adolescence. However, stability of parental preferences for future pediatric health states is unknown during the antenatal and neonatal periods and infancy. OBJECTIVE: To determine whether preference-based, health-related quality-of-life scores obtained serially from 2 cohorts (women with high-risk pregnancies [antenatal cohort] and mothers of very low-birth-weight newborns [VLBW cohort]) are stable during the first year after birth. DESIGN AND METHODS: Longitudinal cohort study. Participants included 80 high-risk pregnant women recruited at 24 +/- 2 weeks of gestation, and 75 mothers of VLBW infants recruited within 1 week of delivery. We conducted 2 to 3 standardized interviews (antenatally, at 1 week after delivery, and at the 12-month corrected age visit) using the Standard Gamble technique to elicit preferences for 5 pediatric hypothetical health states with varying disabilities. RESULTS: Seventy-three mothers with high-risk pregnancies (91%) and 72 mothers of VLBW infants (96%) completed all scheduled interviews. As expected, preference scores were affected by the level of severity of the hypothetical health states (antenatal cohort, F(4,288) = 87.0 [P<.001]; VLBW cohort, F(4,284) = 64.2 [P<.001]). At each assessment, at least 38% of mothers rated 1 or more health states as worse than death. Repeated-measures analysis showed no change in preference scores over time (antenatal cohort, F(2,144) = 1.3 [P =.29]; VLBW cohort, F(1,71) = 0.7 [P =.42]). Maternal socioemotional factors, infant severity of illness at birth, and global health at 12 months did not affect preference scores. CONCLUSION: In our population, maternal preference scores for disabling health states appear to be stable during the first year of life and are unaffected by key maternal and infant variables.

Adult↗
PubMed2003

Health-related quality of life in children with epilepsy: development and validation of self-report and parent proxy measures.

PURPOSE: To answer a need to include and measure accurately the impact and burden of epilepsy as outcomes of interventions with affected children, we developed and validated self-report and parent-proxy respondent health-related quality of life (HRQL) instruments for preadolescent children with epilepsy. METHODS: We combined qualitative and quantitative research methods. Items were extracted from focus group discussions involving children with epilepsy and their parents. We created scales formatted with alternative paired options of forced responses and used factor analysis to generate relevant subscales and reduce the number of items. We checked internal consistency, assessed test-retest reliability 10-14 days apart, and documented construct validity. RESULTS: A sample of 381 children with epilepsy, age 6-15 years, and their parents independently completed a 67-item questionnaire, from which we chose five items for each subscale. The measures share four subscales, but each measure has an additional distinct subscale. The children and parents could discern differences and report differentially between the various aspects of the HRQL. Internal consistency measured with Cronbach's alpha was acceptable for all subscales; construct validity has been demonstrated from the testing of several hypotheses. Test-retest reliability examined with the intraclass correlation coefficient was satisfactory for the parents and for children age 8 years and older. The correlations between the mothers' and children's responses was poor to moderate. CONCLUSIONS: The data demonstrate sound psychometric properties for both related measures, which are easy to administer for children with epilepsy who are 8 years and older and their parents. The subscales encompass HRQL dimensions judged most important by children with epilepsy for the self-report measure and by parents for the proxy response measure. The parent-proxy measure should be useful as a complement to the child self-report measure in evaluating the validity of parental assessment of the child's health status; in longitudinal outcome research; and in HRQL assessment of children who are unable to respond independently.

Adolescent↗
PubMed2003

Starting at the beginning: an introduction to coefficient alpha and internal consistency.

Cronbach's a is the most widely used index of the reliability of a scale. However, its use and interpretation can be subject to a number of errors. This article discusses the historical development of a from other indexes of internal consistency (split-half reliability and Kuder-Richardson 20) and discusses four myths associated with a: (a) that it is a fixed property of the scale, (b) that it measures only the internal consistency of the scale, (c) that higher values are always preferred over lower ones, and (d) that it is restricted to the range of 0 to 1. It provides some recommendations for acceptable values of a in different situations.

Canada↗
PubMed2003

Being inconsistent about consistency: when coefficient alpha does and doesn't matter.

One of the central tenets of classical test theory is that scales should have a high degree of internal consistency, as evidenced by Cronbach's a, the mean interitem correlation, and a strong first component. However, there are many instances in which this rule does not apply. Following Bollen and Lennox (1991), I differentiate between questionnaires such as anxiety or depression inventories, which are composed of items that are manifestations of an underlying hypothetical construct (i.e., where the items are called effect indicators) and those such as Scale 6 of the Minnesota Multiphasic Personality Inventory (Hathaway & McKinley, 1943) and ones used to tap quality of life or activities of daily living in which the items or subscales themselves define the construct (these items are called causal indicators). Questionnaires of the first sort, which are referred to as scales in this article, meet the criteria of classical test theory, whereas the second type, which are called indexes here, do not. I discuss the implications of this difference for how items are selected, the relationship among the items, and the statistics that should and should not be used in establishing the reliability of the scale or index.

Activities of Daily Living↗
PubMed2002

Comparison of review articles published in peer-reviewed and throwaway journals.

CONTEXT: To compare the quality, presentation, readability, and clinical relevance of review articles published in peer-reviewed and "throwaway" journals. METHODS: We reviewed articles that focused on the diagnosis or treatment of a medical condition published between January 1 and December 31, 1998, in the 5 leading peer-reviewed general medical journals and high-circulation throwaway journals. Reviewers independently assessed the methodologic and reporting quality, and evaluated each article's presentation and readability. Clinical relevance was evaluated independently by 6 physicians. RESULTS: Of the 394 articles in our sample, 16 (4.1%) were peer-reviewed systematic reviews, 135 (34.3%) were peer-reviewed nonsystematic reviews, and 243 (61.7%) were nonsystematic reviews published in throwaway journals. The mean (SD) quality scores were highest for peer-reviewed articles (0.94 [0.09] for systematic reviews and 0.30 [0.19] for nonsystematic reviews) compared with throwaway journal articles (0.23 [0.03], F(2,391) = 280.8, P<.001). Throwaway journal articles used more tables (P =.02), figures (P =.01), photographs (P<.001), color (P<.001), and larger font sizes (P<.001) compared with peer-reviewed articles. Readability scores were more often in the college or higher range for peer-reviewed journals compared with the throwaway journal articles (104 [77.0%] vs 156 [64.2%]; P =.01). Peer-reviewed article titles were judged less relevant to clinical practice than throwaway journal article titles (P<.001). CONCLUSIONS: Although lower in methodologic and reporting quality, review articles published in throwaway journals have characteristics that appeal to physician readers.

Consumer Behavior↗
PubMed2002

Effects of rising tuition fees on medical school class composition and financial outlook.

BACKGROUND: Since 1997, tuition has more than doubled at Ontario medical schools but has remained relatively stable in other Canadian provinces. We sought to determine whether the increasing tuition fees in Ontario affected the demographic characteristics and financial outlook of medical students in that province as compared with those of medical students in the rest of Canada. METHODS: As part of a larger Internet survey of all students at Canadian medical schools outside Quebec, conducted in January and February 2001, we compared the respondents from Ontario schools with those from the other schools (control group). Respondents were asked about their age, sex, self-reported family income (as a direct indicator of socioeconomic status), the first 3 digits of their postal code at graduation from high school (as an indirect indicator of socioeconomic status), and importance of financial considerations in choosing a specialty and location of practice. We used logistic regression models to see if temporal changes (1997 v. 2000) among Ontario medical students differed from those among medical students elsewhere in Canada apart from Quebec. RESULTS: Responses were obtained from 2994 (68.5%) of 4368 medical students. Across the medical schools, there was an increase in self-reported family income between 1997 and 2000 (p = 0.03). In Ontario, the proportion of respondents with a family income of less than $40,000 declined from 22.6% to 15.0%. However, compared with the control respondents, the overall rise in family income among Ontario students was not statistically significant. First-year Ontario students reported higher levels of expected debt at graduation than did graduating students (median $80,000 v. $57,000) (p < 0.001), and the proportion of students expecting to graduate with debt of at least $100,000 more than doubled. Neither of these differences was observed in the control group. First-year Ontario students were also more likely than fourth-year Ontario students to report that their financial situation was "very" or "extremely" stressful and to cite financial considerations as having a major influence on specialty choice or practice location. These differences were not observed in the control group. INTERPRETATION: At Canadian medical schools, there are fewer students from low-income families in general. However, Ontario medical students report a large increase in expected debt on graduation, an increased consideration of finances in deciding what or where to practise, and increasing financial stress, factors that are not observed among students in other provinces.

Adult↗
PubMed2002

Characteristics of first-year students in Canadian medical schools.

BACKGROUND: The demographic and socioeconomic profile of medical school classes has implications for where people choose to practise and whether they choose to treat certain disadvantaged groups. We aimed to describe the demographic and socioeconomic characteristics of first-year Canadian medical students and compare them with those of the Canadian population to determine whether there are groups that are over- or underrepresented. Furthermore, we wished to test the hypothesis that medical students often come from privileged socioeconomic backgrounds. METHODS: As part of a larger Internet survey of all students at Canadian medical schools outside Quebec, conducted in January and February 2001, first-year students were asked to give their age, sex, self-described ethnic background using Statistics Canada census descriptions and educational background. Postal code at the time of high school graduation served as a proxy for socioeconomic status. Respondents were also asked for estimates of parental income and education. Responses were compared when possible with Canadian age-group-matched data from the 1996 census. RESULTS: Responses were obtained from 981 (80.2%) of 1223 first-year medical students. There were similar numbers of male and female students (51.1% female), with 65% aged 20 to 24 years. Although there were more people from visible minorities in medical school than in the Canadian population (32.4% v. 20.0%) (p < 0.001), certain minority groups (black and Aboriginal) were underrepresented, and others (Chinese, South Asian) were overrepresented. Medical students were less likely than the Canadian population to come from rural areas (10.8% v. 22.4%) (p< 0.001) and were more likely to have higher socioeconomic status, as measured by parents' education (39.0% of fathers and 19.4% of mothers had a master's or doctoral degree, as compared with 6.6% and 3.0% respectively of the Canadian population aged 45 to 64), parents' occupation (69.3% of fathers and 48.7% of mothers were professionals or high-level managers, as compared with 12.0% of Canadians) and household income (15.4% of parents had annual household incomes less than $40,000, as compared with 39.7% of Canadian households; 17.0% of parents had household incomes greater than $160,000, as compared with 2.7% of Canadian households with an income greater than $150,000). Almost half (43.5%) of the medical students came from neighbourhoods with median family incomes in the top quintile (p < 0.001). A total of 57.7% of the respondents had completed 4 years or less of postsecondary studies before medical school, and 29.3% had completed 6 or more years. The parents of the medical students tended to have occupations with higher social standing than did working adult Canadians; a total of 15.6% of the respondents had a physician parent. INTERPRETATION: Canadian medical students differ significantly from the general population, particularly with regard to ethnic background and socioeconomic status.

Adult↗
PubMed2002

Measuring comorbidity in patients with head and neck cancer.

BACKGROUND: Comorbidities are diseases or conditions that coexist with a disease of interest. The importance of comorbidities is that they can alter treatment decisions, change resource utilization, and confound the results of survival analysis. OBJECTIVE: The objective of this study was to determine the best comorbidity index to use in survival analysis of patients with squamous cell carcinoma of the head and neck. METHOD: Four validated indexes, with very different methodologies (i.e., the Charlson Index, the Cumulative Illness Rating Scale, the Kaplan-Feinstein Classification, the Index of Co-existent Disease), were tested using data from 379 unselected consecutive patients with complete 3-year follow-up from the Kingston Regional Cancer Center. Kaplan-Meier analysis and Cox Proportional Hazards Regression were used to stratify patients into three levels of increasing severity of comorbidity for each index. The Proportion of Variance Explained and Receiver Operating Characteristics curves were used to compare the performance of the indexes. CONCLUSION: The Kaplan-Feinstein Classification was the most successful in stratifying patients in this population.

Adult↗
PubMed2002

Relation of blood counts during clozapine treatment to serum concentrations of clozapine and nor-clozapine.

OBJECTIVE: To determine the relation between serum clozapine and nor-clozapine levels and blood cell counts during clozapine treatment. METHOD: We undertook a prospective longitudinal study of 37 consecutive patients with a diagnosis of schizophrenia treated with clozapine. We obtained informed consent and then determined serum concentrations of clozapine and nor-clozapine weekly. Clozapine was administered daily in divided doses given every 12 hours and adjusted according to clinical guidelines for its use. Samples for serum concentrations were taken at steady state, immediately before the next morning's dose, for 4 to 8 weeks. Complete blood counts (CBC), weight, and vital signs (that is, blood pressure, pulse, and temperature) were also monitored weekly before the morning's dose of clozapine was administered. RESULTS: Analyses of variance showed no significant changes over the 8-week treatment course in the observed mean white blood count (WBC), red blood count (RBC), neutrophils, and lymphocytes counts, or in the hemoglobin and hematocrit. Only a few weak correlations (r < 0.21) were found between these hematological parameters and the measures of serum clozapine and nor-clozapine. CONCLUSIONS: The mechanism of clozapine-induced hematotoxicity at the therapeutic dosage range is probably not by direct toxicity of clozapine or nor-clozapine to the blood cells or their precursors. The formation of the cytotoxic nitrenium compound from clozapine by neutrophils may be necessary.

Adolescent↗
PubMed2002

Breaking up is hard to do: the heartbreak of dichotomizing continuous data.

Researchers often take variables that are measured on a continuum and then break them into categories (for example, above or below some cut-point), either to place subjects into groups or as an outcome measure. In this article, we show that the rationales given for this practice are weak and that categorization results in lost information, reduced power of statistical tests, and increased probability of a Type II error. Dichotomizing a continuous variable is justified only when the distribution of that variable is highly skewed or its relation with another variable is nonlinear.

Bias↗
PubMed2002

The 2 "Es" of research: efficacy and effectiveness trials.

Studies that investigate the usefulness of various therapies fall along a continuum that ranges from those looking at whether an intervention can work under ideal circumstances (efficacy trials) to those that focus on whether a treatment works when applied in the real world (effectiveness trials). Whether a study is closer to one end of the spectrum or the other affects almost every aspect of the trial. These aspects include which patients are eligible for enrollment, the degree of control over the way the intervention is delivered, which patients are or are not included in the analyses, how missing data are handled, and even which statistical tests may be used. The 2 types of trials may yield different results, but both provide useful information. This paper explores these issues, shows the decisions researchers must take at each phase of a trial, and discusses how clinicians should interpret the results.

Clinical Trials as Topic↗
PubMed2002

Antidepressants and the risk of breast cancer.

BACKGROUND: A recent national newspaper article highlighted 2 published research papers that suggest an association between antidepressants and an increased risk of breast cancer. The authors of the 2 papers recommend switching or avoiding the antidepressants implicated in their studies. METHOD: We critically review these papers and, based on our review, consider what clinical practices, if any, should be modified as a result of their findings. RESULTS: Both articles are based upon case-control studies. In the first paper, the authors examine the relation between tricyclic antidepressants (TCAs) and an increased risk of breast cancer. The study upon which the paper is based has several design strengths, and the paper presents findings that have biological plausibility. However, the conclusions are weakened by the lack of accounting for potential confounding factors and multiple statistical comparisons. In the second paper, the authors combined survey and administrative data to examine the association between antidepressant use and breast cancer risk. The press article notwithstanding, the second paper does not find a significant association between specific antidepressants and an increased risk of breast cancer, after adjusting for potential confounders. There are significant methodological limitations to the research upon which the paper is based. CONCLUSIONS: The finding of an association between TCA use and increased risk of breast cancer merits further testing using stronger research designs. However, because of the methodological concerns described, the 2 papers we review provide insufficient evidence to guide practitioners to change clinical practice.

Adult↗
PubMed2002

The case of the missing data: methods of dealing with dropouts and other research vagaries.

Missing data are common in most studies, especially when subjects are followed over time. This can jeopardize the validity of a study because of reduced power to detect differences, and especially because subjects who are lost to follow-up rarely represent the group as a whole. There are several approaches to handling missing data, but some may result in biased estimates of the treatment effect, and others may overestimate the significance of the statistical tests. When cross-sectional data (for example, demographic and background information and a single outcome measurement time) are missing, replacement with the group mean leads to an underestimate of the standard deviation (SD) and inflation of the Type I error rate. Using regression estimates, especially with error built into the imputed value, lessens but does not eliminate this problem. Multiple imputation preserves the estimates of both the mean and the SD, even when a significant proportion of the data are missing. With longitudinal studies, the last observation carried forward (LOCF) approach preserves the sample size, but may make unwarranted assumptions about the missing data, resulting in either underestimating or overestimating the treatment effects. Growth curve analysis makes maximal use of the existing data and makes fewer assumptions.

Clinical Trials as Topic↗
PubMed2002

Do hospital E-codes consistently capture suicidal behaviour?

Hospital separation data are used to study suicidal behaviour; however, there is little information about the appropriateness of these data for research and planning activities. The study purpose is to examine how consistently hospital separation E-code data reflect suicidal behaviours. Expert clinicians reviewed medical records of individuals who had a separation for self-poisoning to determine whether the self-poisoning was deliberate. Agreement among clinicians was evaluated and latent class analysis performed to derive a summary estimate of the prevalence of deliberate self-poisoning. This estimate was then compared to the prevalence of deliberate self-poisoning based on the external cause of injury (E-codes). Clinicians estimated the prevalence to be 63% higher than the E-code based prevalence. Much larger discrepancies were apparent among older age groups, those whose care was primarily medical in nature and those with a longer length of hospital stay. In acute care settings, self-poisonings among the elderly may not receive adequate attention and/or documentation. Estimating the prevalence of admissions for suicidal behaviour using hospital separation data is of questionable validity, particularly among older age groups.

Adolescent↗