Biomedical subjects

Pascale Tubert-Bitter

Publications and source records attributed to Pascale Tubert-Bitter.

10 recordsLinked to original sources

PubMed2025

Covid-19 Vaccination During Pregnancy in France: a Descriptive Study of Uptake Using the National Healthcare data System.

Pregnant women and their fetus are at increased risk of complications when infected by SARS-CoV-2. This study describes COVID-19 vaccine uptake during pregnancy in France (i) according to socio-demographic characteristics, and (ii) over calendar time and pregnancy stages. Using the hospital discharge records of the national healthcare database, we identified women ending pregnancy at hospital between Dec 27, 2020, i.e. beginning of Covid-19 vaccine availability, and Dec 31, 2022. Covid-19 vaccinations and SARS-CoV-2 infections were also available on two specific linked databases. Vaccine coverage was defined as uptake of at least one dose of vaccine during the 2-year study period, or more specifically during one of five phases of pregnancy (first, second and third trimesters, pre-conceptional and post-pregnancy periods). We also defined ineligibility as the six-month period following each Covid-19 infection. We calculated weekly rates of vaccination by pregnancy phase, accounting for ineligibility. About 75% of women received at least one dose of vaccine in 2021-2022 vs. 90% in the general population with a similar age structure. About 26% received at least one dose of vaccine while pregnant. The rate was lower among younger women, deprived women, and those living in the south-east of mainland France or in overseas territories. Weekly vaccination rates according to the phase of pregnancy showed that women mostly received vaccination outside the pregnancy trimesters (after or, to a less extent, before pregnancy). Vaccinations during pregnancy mostly occurred in the second trimester. When only elective terminations were considered, weekly rates of vaccination were almost identical, whatever the pregnancy phase (before, during or after pregnancy). Overall, our results show the positive impact of national recommendations on uptake dynamics. Vaccine coverage in pregnant women could be improved with targeted campaigns.

Humans↗

PubMed2007

A combined superiority and non-inferiority approach to multiple endpoints in clinical trials.

Treatment comparisons in clinical trials often involve multiple endpoints. By making use of bootstrap tests, we develop a new non-parametric approach to multiple-endpoint testing that can be used to demonstrate non-inferiority of a new treatment for all endpoints and superiority for some endpoint when it is compared to an active control. It is shown that this approach does not incur a large multiplicity cost in sample size to achieve reasonable power and that it can incorporate complex dependencies in the multivariate distributions of all outcome variables for the two treatments via bootstrap resampling.

Algorithms↗

PubMed2005

Testing independence between two Poisson-generated multinomial variables in case-series and cohort studies.

In case-series or cohort studies, we propose a test of independence between the occurrences of two types of recurrent events (such as two repeated infections) related to an intermittent exposure (such as an antibiotic treatment). The test relies upon an extension of a recent method for analysing case-series data, in the presence of one type of recurrent event. The test statistic is derived from a bivariate Poisson generated-multinomial distribution. Simulations for checking the validity of the test concerning the type I error and the power properties are presented. The test is illustrated using data from a cohort on antibiotics bacterial resistance in schoolchildren.

Anti-Bacterial Agents↗

PubMed2005

An easy to use method to approximate Poisson confidence limits.

Despite the ever larger choice of softwares and statistical packages allowing fast and accurate computation of binomial and Poisson confidence limits, there is always a need for a simple and reliable formula allowing non-computerized computations. The method proposed in this paper is derived from the Freeman and Tukey's variance stabilizing transformation for a random Poisson variable and adjusted for giving the best fit with the exact Poisson values. Despite its simplicity, allowing its use in any circumstances, this method provides very satisfactory results and a much better fit than classical formula based on the normal approximation, even if a continuity correction is used. It allows computation of Poisson confidence limits both for count or rates and proportions.

Biometry↗

PubMed2005

A nonparametric comparison of the effectiveness of treatments: a multivariate toxicity-penalized approach.

In cancer clinical trials, the amount of treatment dose actually received by a patient may be limited by severe toxicity or lack of efficacy. A nonparametric approach is proposed for comparing the effectiveness of treatments based on the bivariate relationship defined by the doses at which efficacy and toxicity are observed to occur. Simulation studies are used to contrast the performance of the new procedure with the usual method of comparing percentages of patients who have effective results. Data from a randomized clinical trial of patients with metastatic nonseminomatous germ cell tumors are used to illustrate the method.

Antineoplastic Agents↗

PubMed2005

Evaluation of statistical association measures for the automatic signal generation in pharmacovigilance.

Pharmacovigilance aims at detecting the adverse effects of marketed drugs. It is generally based on the spontaneous reporting of events thought to be the adverse effects of drugs. Spontaneous Reporting Systems (SRSs) supply huge databases that pharmacovigilance experts cannot exhaustively exploit without data mining tools. Data mining methods; i.e., statistical association measures in conjunction with signal generation criteria, have been proposed in the literature but there is no consensus regarding their applicability and efficiency, especially since such methods are difficult to evaluate on the basis of actual data. The objective of this paper is to evaluate association measures on simulated datasets obtained with SRS modeling. We compared association measures using the percentage of false positive signals among a given number of the most highly ranked drug-event combinations according to the values of the association measures. By considering 150 drugs and 100 adverse events, these percentages of false positives, among the 500 most highly ranked drug-event couples, vary from 1.1% to 53.4% (averages over 1000 simulated datasets). As the measures led to very different results, we could identify which measures appeared to be the most relevant for pharmacovigilance.

Adverse Drug Reaction Reporting Systems↗

PubMed2005

Trends in spontaneous adverse drug reaction reports to the French pharmacovigilance system (1986-2001).

BACKGROUND: The French pharmacovigilance system is based on a network of 31 regional centres located in teaching hospitals and coordinated by the French Medicines Agency ("Agence Française de Sécurité Sanitaire des Produits de Santé" [Afssaps]). Since 1984, they have shared a common database of adverse drug reactions (ADRs) that are spontaneously reported by healthcare professionals. The objective of this study is to describe the characteristics of the reports and the reporting trends in the French pharmacovigilance spontaneous reporting database from 1986 to 2001. METHODS: All the reports from January 1986 to December 2001 were included. Drugs and ADRs were translated to anatomical therapeutic chemical (ATC) codes and MedDRA classifications, respectively. RESULTS: The total number of reports was 197 580 over the 16-year period, with linearly increase over time. The median (interquartile range [IQR]) age of the patients was 53 (34-70) and the male/female ratio was 0.82. The median (IQR) time between the date of occurrence of the ADR and the date of report was 73 days (34-166). The reporter was a specialist in 74% of the reports and a general practitioner in 17%. The annual rate of reporting according to medical demography strongly increased for the specialists, especially since 1994. At least one ADR was considered as serious in 44.8% of the reports. The ADRs were most frequently related to nervous system drugs (23%), followed by cardiovascular drugs (19%) and systemic anti-infectives (17%). The latter class had the fastest progression mostly due to antiretroviral therapy since 1996. According to the Medical Dictionary for Regulatory Activities (MedDRA) coding, the system organ most often reported was skin and subcutaneous tissue disorders (29%), followed by nervous system disorders (19%), gastrointestinal disorders (12%), blood and lymphatic system disorders (12%), vascular disorders (12%) and general disorders and administration site conditions (12%). DISCUSSION: All spontaneous reporting systems are affected by under-reporting. One of their goals is to generate early signals, which might be more affected by reporting bias than by under-reporting. Some improvements should be made in the design of the French database, but data collected since 1986 constitute an essential tool for the routine work of the 31 pharmacovigilance centres. CONCLUSION: This first description of the data of the French pharmacovigilance database involving all drugs and ADRs shows an increasing tendency to reporting over time, especially in specialists and for systemic anti-infective drugs. The database that uses hierarchical international classifications for drugs and adverse reactions may be used for further studies and could be the basis for an automatic signal generation system.

Adult↗

PubMed2003

Two-treatment comparison based on joint toxicity and efficacy ordered alternatives in cancer trials.

The primary goal of anticancer treatments is to attain efficacy, however toxicity could affect the course of the therapy. Methods have been proposed for comparing two treatments on the basis of the joint distribution for safety and efficacy outcomes, but they do not take into account the cumulative doses of drugs (chemotherapy) or radiation (radiotherapy) received by each patient. Moreover, these methods assume a parametric form for the joint distribution. In this paper we define a multi-dimensional parameter including toxicity and efficacy outcomes and the dose at which one, none or both occur. Each patient is classified into an ordered category depending on the order of occurrence of these two criteria: the sooner the patient benefits from efficacy and/or the later he/she experiences toxicity, the better is the treatment. We then apply likelihood ratio tests with ordered alternatives. This procedure requires constrained maximum likelihood estimation via isotonic regression. A large set of simulations compares the proposed tests to other more usual tests and the results show a good power and a satisfactory type I error control. Our approach is illustrated with a multi-centre randomized clinical trial involving patients with metastatic non-seminomatous germ cell tumours.

Antineoplastic Agents↗

PubMed2003

A simple method to estimate sample sizes for safety equivalence studies using inverse sampling.

Safety equivalence studies may be required to demonstrate that a new procedure or process is at least as safe as a previous one. They usually involve low or very low outcome rates that are often not precisely determined, making patient-based sample sizing uncertain. Using a reverse sampling approach, a method is derived from standard equations to estimate the number of events that need to be observed to demonstrate equivalence using the confidence interval approach. For instance, for a one-sided (nonsuperiority) hypothesis, 5% alpha risk, and 80% power, almost 100 events need to be observed in each study arm to demonstrate equivalence within 30%, or 250 events for 20% equivalence. The number of patients to be included can be derived directly from expected event rates.

Confidence Intervals↗

PubMedDate not supplied

The safety of drugs for OTC use: what evidence is required for an NSAID switch?

In recent years there has been a growing demand for safe and effective over-the-counter (OTC) drugs. The demonstration of the safety of OTC products in actual conditions of use is crucial for their wide distribution, since the circumstances of their use may be different from the prescription-only setting. A group of experts met in Geneva, Switzerland, with the aim of exploring the criteria required to show safety equivalence of OTC medications, with specific reference to low-dose non-steroidal anti-inflammatory drugs (NSAIDs) used for analgesia. It was agreed that an acceptable surrogate marker for safety as the primary endpoint in a study designed to show that a new NSAID was not inferior to a current NSAID would be any adverse event leading the patient to consult a physician. A sample size of 10,000 patients in each arm of a two-arm study would be sufficient to show non-inferiority with acceptable relative risk equal to 1.2 with at least 90% power for an event rate of 5%. An example of a possible pharmacy-based randomized study design to demonstrate safety equivalence of OTC analgesics is given.

Anti-Inflammatory Agents, Non-Steroidal↗