Biomedical subjects

C Sakarovitch

Publications and source records attributed to C Sakarovitch.

8 recordsLinked to original sources

PubMed2006

Improved knowledge and practices among end-users of mother-to-child transmission of HIV prevention services in rural Zimbabwe.

OBJECTIVE: To evaluate the influence of a prevention of mother-to-child transmission of HIV advocacy and mobilization campaign on awareness and knowledge levels within the community. METHOD: We used a knowledge, attitudes and practices survey to collect baseline data in November 2002 and again in July 2004 for evaluation purposes. RESULTS: A total of 351 women attending healthcare services were interviewed each time. The proportion of women aware of the service increased from 48.0% in 2002 to 82.8% in 2004 (OR = 4.9, 95% CI 3.3-7.3, P = 0.001). Exclusive breastfeeding was identified as a mother-to-child transmission risk factor by 27.1% in 2002 and by 55.8% of respondents in 2004 (OR = 2.9, CI 2.1-4.2, P = 0.001). Although most interviewees agreed that the prevention of sexual transmission of HIV was the best strategy for prevention of mother-to-child transmission of HIV (88.3% in 2002 and 96.4% in 2004), few reported having ever used a male condom (24.8% in 2002 vs. 29.8% in 2004, P = 0.16). DISCUSSION: Prevention of mother-to-child transmission of HIV strategies at both individual and community level were still insufficiently understood and applied. Targeted educational messages and communication for social change need to be combined. Knowledge, attitudes and practices surveys can be used to monitor programme progress.

Adult↗

PubMed2005

Indirect comparisons of competing interventions.

OBJECTIVES: To survey the frequency of use of indirect comparisons in systematic reviews and evaluate the methods used in their analysis and interpretation. Also to identify alternative statistical approaches for the analysis of indirect comparisons, to assess the properties of different statistical methods used for performing indirect comparisons and to compare direct and indirect estimates of the same effects within reviews. DATA SOURCES: Electronic databases. REVIEW METHODS: The Database of Abstracts of Reviews of Effects (DARE) was searched for systematic reviews involving meta-analysis of randomised controlled trials (RCTs) that reported both direct and indirect comparisons, or indirect comparisons alone. A systematic review of MEDLINE and other databases was carried out to identify published methods for analysing indirect comparisons. Study designs were created using data from the International Stroke Trial. Random samples of patients receiving aspirin, heparin or placebo in 16 centres were used to create meta-analyses, with half of the trials comparing aspirin and placebo and half heparin and placebo. Methods for indirect comparisons were used to estimate the contrast between aspirin and heparin. The whole process was repeated 1000 times and the results were compared with direct comparisons and also theoretical results. Further detailed case studies comparing the results from both direct and indirect comparisons of the same effects were undertaken. RESULTS: Of the reviews identified through DARE, 31/327 (9.5%) included indirect comparisons. A further five reviews including indirect comparisons were identified through electronic searching. Few reviews carried out a formal analysis and some based analysis on the naive addition of data from the treatment arms of interest. Few methodological papers were identified. Some valid approaches for aggregate data that could be applied using standard software were found: the adjusted indirect comparison, meta-regression and, for binary data only, multiple logistic regression (fixed effect models only). Simulation studies showed that the naive method is liable to bias and also produces over-precise answers. Several methods provide correct answers if strong but unverifiable assumptions are fulfilled. Four times as many similarly sized trials are needed for the indirect approach to have the same power as directly randomised comparisons. Detailed case studies comparing direct and indirect comparisons of the same effect show considerable statistical discrepancies, but the direction of such discrepancy is unpredictable. CONCLUSIONS: Direct evidence from good-quality RCTs should be used wherever possible. Without this evidence, it may be necessary to look for indirect comparisons from RCTs. However, the results may be susceptible to bias. When making indirect comparisons within a systematic review, an adjusted indirect comparison method should ideally be used employing the random effects model. If both direct and indirect comparisons are possible within a review, it is recommended that these be done separately before considering whether to pool data. There is a need to evaluate methods for the analysis of indirect comparisons for continuous data and for empirical research into how different methods of indirect comparison perform in cases where there is a large treatment effect. Further study is needed into when it is appropriate to look at indirect comparisons and when to combine both direct and indirect comparisons. Research into how evidence from indirect comparisons compares to that from non-randomised studies may also be warranted. Investigations using individual patient data from a meta-analysis of several RCTs using different protocols and an evaluation of the impact of choosing different binary effect measures for the inverse variance method would also be useful.

Bias↗

PubMed2003

Pepsinogen A, pepsinogen C, and gastrin as markers of atrophic chronic gastritis in European dyspeptics.

Serum levels of pepsinogen and gastrin are parameters that can be used as biomarkers for gastric mucosa. The aim of this study was to validate these serum biomarkers, that is pepsinogen A (PGA), pepsinogen C (PGC), PGA/PGC ratio, and gastrin, as screening tests for precancerous lesions: atrophic chronic gastritis (ACG) or Helicobacter pylori-related corpus-predominant or multifocal atrophy. The study population was comprised of a subsample of 284 patients from the 451 included in the Eurohepygast cohort, between 1995 and 1997. The concentrations of PGA, PGC, and gastrin were measured by radioimmunoassays. Histological diagnosis was the gold standard. Cut-off points were calculated using receiving operator characteristics (ROC) curves. Factors linked to variation of biomarkers were identified using multivariate linear regression. The mean of each biomarker in the sample was: PGA, 77.4 microg x l(-1); PGC, 13.2 microg x l(-1); PGA/PGC, 6.7; and gastrin, 62.4 ng x l(-1). For ACG patients, the areas under the PGA, PGC, PGA/PGC, and gastrin ROC curves were 0.55, 0.62, 0.73, and 0.58, respectively. The best cut-off point for PGA/PGC was 5.6, with sensitivity 65% and specificity 77.9%. For H. pylori-related corpus-predominant or multifocal atrophy, the areas under the respective ROC curves were 0.57, 0.67, 0.84, and 0.69. The best cut-off point for PGA/PGC was 4.7, with sensitivity 77.1% and specificity 87.4%. The results suggested that only the PGA/PGC ratio can be considered as a biomarker for precancerous lesions of the stomach, and may be useful as a screening test.

Antigens, Bacterial↗

PubMed2003

Bootstrap choice of estimators in parametric and semiparametric families: an extension of EIC.

Ishiguro, Sakamoto, and Kitagawa (1997, Annals of the Institute of Statistical Mathematics 49, 411-434) proposed EIC as an extension of Akaike criterion (AIC); the idea leading to EIC is to correct the bias of the log-likelihood, considered as an estimator of the Kullback-Leibler information, using bootstrap. We develop this criterion for its use in multivariate semiparametric situations, and argue that it can be used for choosing among parametric and semiparametric estimators. A simulation study based on aregression model shows that EIC is better than its competitors although likelihood cross-validation performs nearly as well except for small sample size. Its use is illustrated by estimating the mean evolution of viral RNA levels in a group of infants infected by HIV.

Age Factors↗

PubMed2003

Evaluating non-randomised intervention studies.

OBJECTIVES: To consider methods and related evidence for evaluating bias in non-randomised intervention studies. DATA SOURCES: Systematic reviews and methodological papers were identified from a search of electronic databases; handsearches of key medical journals and contact with experts working in the field. New empirical studies were conducted using data from two large randomised clinical trials. METHODS: Three systematic reviews and new empirical investigations were conducted. The reviews considered, in regard to non-randomised studies, (1) the existing evidence of bias, (2) the content of quality assessment tools, (3) the ways that study quality has been assessed and addressed. (4) The empirical investigations were conducted generating non-randomised studies from two large, multicentre randomised controlled trials (RCTs) and selectively resampling trial participants according to allocated treatment, centre and period. RESULTS: In the systematic reviews, eight studies compared results of randomised and non-randomised studies across multiple interventions using meta-epidemiological techniques. A total of 194 tools were identified that could be or had been used to assess non-randomised studies. Sixty tools covered at least five of six pre-specified internal validity domains. Fourteen tools covered three of four core items of particular importance for non-randomised studies. Six tools were thought suitable for use in systematic reviews. Of 511 systematic reviews that included non-randomised studies, only 169 (33%) assessed study quality. Sixty-nine reviews investigated the impact of quality on study results in a quantitative manner. The new empirical studies estimated the bias associated with non-random allocation and found that the bias could lead to consistent over- or underestimations of treatment effects, also the bias increased variation in results for both historical and concurrent controls, owing to haphazard differences in case-mix between groups. The biases were large enough to lead studies falsely to conclude significant findings of benefit or harm. Four strategies for case-mix adjustment were evaluated: none adequately adjusted for bias in historically and concurrently controlled studies. Logistic regression on average increased bias. Propensity score methods performed better, but were not satisfactory in most situations. Detailed investigation revealed that adequate adjustment can only be achieved in the unrealistic situation when selection depends on a single factor. CONCLUSIONS: Results of non-randomised studies sometimes, but not always, differ from results of randomised studies of the same intervention. Non-randomised studies may still give seriously misleading results when treated and control groups appear similar in key prognostic factors. Standard methods of case-mix adjustment do not guarantee removal of bias. Residual confounding may be high even when good prognostic data are available, and in some situations adjusted results may appear more biased than unadjusted results. Although many quality assessment tools exist and have been used for appraising non-randomised studies, most omit key quality domains. Healthcare policies based upon non-randomised studies or systematic reviews of non-randomised studies may need re-evaluation if the uncertainty in the true evidence base was not fully appreciated when policies were made. The inability of case-mix adjustment methods to compensate for selection bias and our inability to identify non-randomised studies that are free of selection bias indicate that non-randomised studies should only be undertaken when RCTs are infeasible or unethical. Recommendations for further research include: applying the resampling methodology in other clinical areas to ascertain whether the biases described are typical; developing or refining existing quality assessment tools for non-randomised studies; investigating how quality assessments of non-randomised studies can be incorporated into reviews and the implications of individual quality features for interpretation of a review's results; examination of the reasons for the apparent failure of case-mix adjustment methods; and further evaluation of the role of the propensity score.

Bias↗

PubMed2002

Suicide in female nurses in England and Wales.

BACKGROUND: Female nurses appear to have an increased risk of suicide but the reasons are unknown. METHOD: We have concluded a study of nurse suicides (N = 106) in England and Wales, including a psychological autopsy study (N = 42) and case-control comparison with living nurses (N = 84). RESULTS: Nearly three-quarters of the nurse suicides had previous contact with psychiatric services and almost half had been psychiatric in-patients in the past. There were particularly marked differences between the cases and controls for current psychiatric disorder (90.5% v. 7.1%, OR = 68.5), personality disorder (38.1% v. 12%, OR = 32), and history of deliberate self-harm (71.4% v. 2.4%, OR = 58.5). Family background and social factors (especially concerning interpersonal relationships) also distinguished the two groups. Smoking and serious alcohol abuse were much more frequent in the suicides. There was some indication that while many of the suicides were in contact with psychiatric services, care may not have been optimal in some cases. CONCLUSIONS: The most important strategies for suicide prevention in nurses are in prevention, detection and management of psychiatric disorders. In assessing suicide risk a history of DSH and the presence of comorbid psychiatric and personality disorders are particularly important.

Adult↗

PubMed2001

Helicobacter pylori infection in patients consulting gastroenterologists in France: prevalence is linked to gender and region of residence.

BACKGROUND: Because of limited data on the epidemiology of Helicobacter pylori in France, the prevalence of this infection by region and its associated risk factors were studied between 1995 and 1997 among patients consulting a representative sample of gastroenterologists by region. METHOD: A cross-sectional study was performed. Patients consulting gastroenterologists for whatever reason were screened for H. pylori infection determined by specific salivary IgG. A questionnaire was filled out by the gastroenterologist. A multivariate analysis was performed with all relevant variables. RESULTS: 3,153 patients were included. The mean age was 48.5 years; 51.8% were women. After stratification by patients consulting for upper digestive tract (UDT) and non-UDT symptoms, H. pylori infection was found to be more prevalent, in both groups, for characteristics such as being born in a developing country, overcrowding during childhood, and primary educational level. Interestingly, gender (odds ratio OR(UDT for women) = 0.7 (95% CI 0.5-0.8] and OR(non-UDT) for women = 0.6 [95% CI 0.5-0.8]) and living in a region other than the south-west (OR(UDT) varying from 1.5 to 2.0 and OR(non-UDT) varying from 1.3 to 2.1, depending on the region) was associated with the odds of prevalent infection. CONCLUSION: These findings show (1) that gender deserves more attention in the epidemiology of H. pylori and (2) a regional disparity in France regarding H. pylori infection.

Adolescent↗

PubMed2001

Suicide in doctors: a study of risk according to gender, seniority and specialty in medical practitioners in England and Wales, 1979-1995.

STUDY OBJECTIVE: To investigate the suicide risk of doctors in England and Wales, according to gender, seniority and specialty. DESIGN: Retrospective cohort study. Suicide rates calculated by gender, age, specialty, seniority and time period. Standardised mortality ratios calculated for suicide (1991-1995), adjusted for age and sex. SETTING: England and Wales. SUBJECTS: Doctors in the National Health Service who died by suicide between 1979 and 1995, identified by death certificates. Population at risk based on Department of Health manpower data. MAIN RESULTS: Two hundred and twenty three medical practitioners in the National Health Service who died by suicide or undetermined cause were identified. The annual suicide rates in male and female doctors were 19.2 and 18.8 per 100 000 respectively. The suicide rate in female doctors was higher than in the general population (SMR 201.8; 95% CI 99.7, 303.9), whereas the rate in male doctors was less than that of the general population (SMR 66.8; 95% CI 46.6, 87.0). The difference between the mortality ratios of the female and male doctors was statistically significant (p=0.01), although the absolute suicide risk was similar in the two genders. There were significant differences between specialties (p=0.0001), with anaesthetists, community health doctors, general practitioners and psychiatrists having significantly increased rates compared with doctors in general hospital medicine. There were no differences with regard to seniority and time period. CONCLUSIONS: There is an increased risk of suicide in female doctors, but male doctors seem to be at less risk than men in the general population. The excess risk of suicide in female doctors highlights the need to tackle stress and mental health problems in doctors more effectively. The risk requires particular monitoring in the light of the very large increase in the numbers of women entering medicine.

Adult↗