[Evaluation of vision quality after laser vision correction in healthcare professionals]. / Évaluation de la qualité de vision après chirurgie réfractive au laser chez les professionnels de santé.

PURPOSE: Healthcare professionals require good quality of vision. The main objective of this study is to evaluate the satisfaction and vision quality after laser vision correction in healthcare professionals. METHODS: This is a monocentric retrospective study. An online 25-question survey was sent to ametropic physicians, surgeons and nurses who underwent corneal refractive surgery with laser-assisted in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) between July 2012 and February 2016. Questionnaire responses were recorded anonymously by the internet survey site. These patients' pre- and postoperative data were analyzed. RESULTS: In total, 2491 laser vision corrections were performed during this time frame. One hundred and fifty-eight patients were healthcare providers; 131 received the survey, and 111 responded. Ninety-nine were surgeons, 60 were medical physicians, and 32 were nurses. Ninety-one percent reported that they were satisfied with their postoperative vision quality, 63.9% even reported an improvement in their quality of vision compared with their corrected preoperative vision, 92.8% reported that they would have the procedure again, and 94.6% would recommend the procedure to a family member or a patient. Visual outcomes showed high levels of efficacy and predictability. CONCLUSION: While healthcare professionals require good quality of vision, those who had undergone laser vision correction reported the same satisfaction as the general population and would recommend the procedure to their family, friends and patients.

Psychotropic prescription in non-psychiatric hospital settings.

A study was conducted to assess differences in psychotropic prescription (PP) in various non-psychiatric hospital settings. After adjustment for demographic, medical and psychological status, rates of PP were significantly lower for surgical, intensive care and outpatients and higher for geriatric patients than for patients in other settings, suggesting inadequate consideration of psychiatric problems in certain contexts, in particular intensive care units.

A semiparametric approach for the two-sample comparison of survival times with long-term survivors.

In the two-sample comparison of survival times with long-term survivors, the overall difference between the two distributions reflects differences occurring in early follow-up for susceptible subjects and in long-term follow-up for nonsusceptible subjects. In this setting, we propose statistics for testing (i) no overall, (ii) no short-term, and (iii) no long-term difference between the two distributions to be compared. The statistics are derived as follows. A semiparametric model is defined that characterizes a short-term effect and a long-term effect. By approximating this model about no difference in early survival, a time-dependent proportional hazards model is obtained. The statistics are obtained from this working model. The asymptotic distributions of the statistics for testing no overall or no short-term effects are ascertained, while that of the statistic for testing no long-term effect is valid only when the short-term effect is small. Simulation studies investigate the power properties of the proposed tests for different configurations. The results show the interesting behavior of the proposed tests for situations where a short-term effect is expected. An example investigating the impact of progesterone receptors status on local tumor relapse for patients with early breast cancer illustrates the use of the proposed tests.

Marked 24-h rest/activity rhythms are associated with better quality of life, better response, and longer survival in patients with metastatic colorectal cancer and good performance status.

The rest/activity circadian cycle has been used as a reference for chemotherapy administration at specific times to improve tolerability and efficacy. Because cancer processes may be associated with alterations of circadian rhythms, the rest/activity cycle was monitored noninvasively to assess its relationship with tumor response, survival, and quality of life in 200 patients with metastatic colorectal cancer. Patients wore an actigraph, a wristwatch that records the number of accelerations per minute, for 3 days before receiving chronomodulated chemotherapy. The circadian rhythms in activity were estimated by two robust parameters: the autocorrelation coefficient at 24 h (r24), and the dichotomy index (I

Sample size calculations for risk equivalence testing in pharmacoepidemiology.

Equivalence testing has been widely discussed and is commonly used in pharmacokinetics (bioequivalence) and clinical trials (therapeutic equivalence). It can also be applied to pharmacoepidemiology, where the aim may be to test with a known risk (one-group design) or with another drug (two-group design). Whether the approach is two-sided or one-sided, predefined equivalence limits are required. The definition of the equivalence region can be based on either risk difference or risk ratio. Risk equivalence testing is complicated by the binary nature of the outcome, its low frequency, and by the absence of commonly defined equivalence limits for differences or ratios. In this context, we consider usable formulae for sample sizes. In most cases, at least when the risk studied is large enough (above 1/1,000), it appears that these formulae result in sample sizes that may be acceptable for practical purposes. For example, demonstrating equivalence with a known risk of 0.01, a 20% maximal risk difference, and a one-sided test (alpha = 0.05 and beta = 0.2) requires: under the one-group design (known risk), 15,309 patients; and under the two-group design, 30,617 patients per group. This approach is the appropriate way to conclude equivalence, rather than the commonly used approach of difference testing and concluding equivalence when the null hypothesis of equality is not rejected.

Unobserved covariates in the two-sample comparison of survival times: a maximum efficiency robust test.

In analysing a clinical trial with the logrank test, the hazards between the two groups are usually assumed to be proportional. Nevertheless, this hypothesis is no longer valid with unobserved covariates. As a consequence, there is a loss of power of the logrank test for testing the null hypothesis H(0) of no treatment effect. We propose a test suited for taking into account unobserved covariates. The proposed approach is based on a proportional hazard frailty model whereby the omitted covariates are considered as an unobserved frailty variable. The procedure is as follows. In a first step, the weighted logrank test optimal for testing H(0) against a general proportional hazard frailty model is obtained and its specialization for a gamma frailty variable is derived. In a second step, the proposed test is obtained by combining the maximin efficiency robustness principle and the gamma frailty distribution properties. Simulation studies investigate the power properties of the test for different frailty distributions. A breast cancer clinical trial is analysed as an example. The proposed test might be recommended rather than the logrank for practical situations in which one expects heterogeneity related to omitted covariates.

Prevalence of suicide ideation and suicide attempts in nine countries.

BACKGROUND: There are few cross-national comparisons of the rates of suicide ideation and attempts across diverse countries. Nine independently conducted epidemiological surveys using similar diagnostic assessment and criteria provided an opportunity to obtain that data. METHODS: Suicide ideation and attempts were assessed on the Diagnostic Interview Schedule in over 40000 subjects drawn from the United States, Canada, Puerto Rico, France, West Germany, Lebanon, Taiwan, Korea and New Zealand. RESULTS: The lifetime prevalence rates/100 for suicide ideation ranged from 2.09 (Beirut) to 18.51 (Christchurch, New Zealand). Lifetime prevalence rates/100 for suicide attempts ranged from 0.72 (Beirut) to 5.93 (Puerto Rico). Females as compared to males had only marginally higher rates of suicidal ideation in most countries, reaching a two-fold increase in Taiwan. Females as compared to males had more consistently higher rates for suicide attempts, reaching a two- to three-fold increase in most countries. Suicide ideation and attempts in most countries were associated with being currently divorced/separated as compared to currently married. CONCLUSIONS: While the rates of suicide ideation varied widely by country, the rates of suicide attempts were more consistent across most countries. The variations were only partly explained by variation in rates of psychiatric disorders, divorce or separation among countries and are probably due to cultural features that we do not, as yet, understand.

[Use of GEE for modeling censored correlated data: application to the study of risk factors for withdrawal of totally implantable vascular access devices in cystic fibrosis]. / Utilisation des GEE pour la modélisation de données censurées corrélées: application à l'étude des facteurs de risque de retrait des chambres implantables chez le mucoviscidosique.

BACKGROUND: The proportional hazards model proposed by Cox for modeling censored data is not suited for correlated delays, for instance when several events can be observed on each subject. METHODS: To analyze correlated delays, we propose to use a log-linear marginal model equivalent to Cox model. Correlations are taken into account through the use of Liang and Zeger's Generalized Estimating Equations (GEE) and of their robust variance estimator. An advantage of this method is that it can be implemented through the SAS GENMOD procedure. When ties are observed, we propose to use multiple imputations, creating M data sets without ties from the original one. RESULTS: This method is applied to a retrospective survey on the risk of withdrawing totally implantable vascular access devices (TIVAD) because of complication in cystic fibrosis patients: 265 TIVAD implanted in 200 patients were observed. Risk factors were characteristics of the device or of the patient. Results obtained with the robust variance estimator and ten imputations show that the use of the device for taking blood (vs exclusive perfusion of antibiotics), polyurethane catheter (vs. silicon), use of counterpressure for upkeeping and pulmonary colonization by Pseudomonas Aeruginosa are significantly associated to withdrawal. Under the Cox model which does not account for the correlations, some conclusions differ because the robust variance of the estimators is smaller than the variance obtained under the working assumption of independent delays. CONCLUSION: This approach allows the modeling of correlated survival data with SAS software. Our results illustrate the necessity of accounting for existing correlations.

What happens to depressed men? Application of the Stirling County criteria.

In a recent issue of the Harvard Review of Psychiatry, results from the Stirling County Study showed that the prevalence and incidence rates of depression were similar in men and women when "gender-fair" criteria were used and help-seeking was not required. We attempted to replicate these findings by applying the criteria for depression from the Stirling County Study to two national and six international epidemiologic surveys conducted in the 1980s and 1990s. Depression was defined as dysphoric mood and disturbances of sleep, appetite, and energy, with at least a mild degree of impairment. The rates of depression were computed using this algorithm with data from the US Epidemiologic Catchment Area Study, conducted in the 1980s, the US National Comorbidity Survey, conducted in the 1990s, and independent community surveys from Canada, Puerto Rico, France, Taiwan, Korea, and New Zealand. For the US studies, these rates were recalculated after persons seeking treatment were removed from the analyses, where such data were available. Using Stirling County Study criteria, the lifetime prevalence rate of depression remains approximately twice as high in women as in men cross-nationally, except in Puerto Rico. Excluding help-seeking as a criterion and controlling for birth cohort do not change the findings. The Stirling County findings on absence of a sex difference in rates of depression using "gender-fair" criteria may be due to methodological variance in the collection of data, sample size, or the social and/or genetic uniqueness of the Atlantic Canadian community.

[Estimation methods in a sampling survey]. / Méthodes d'estimation dans une enquête par sondage.

The objective of this paper is to present a guide for statistical analysis of a sampling survey. Advantages and disadvantages of classical sampling designs are first discussed. A sampling survey was designed to give more precise estimates of parameters which characterize a targeted well-defined population. Simple sampling design often is impossible in large population and rarely is the optimal solution. According to practical and economic constraints, and to available sampling frames, other strategies (stratification, unequal probabilities, several selection steps) may be necessary or more efficient. Fundamental tools to compute estimators and their confidence intervals are presented. The choice of the sampling method determine for each population unit the probability to include it in the final sample. These inclusion probabilities must be known to formulate estimators, ideally unbiased and with low variance. Difficulties arise from calculating the variance, especially for estimators which are not linear functions of the characteristics of interest. In that case, estimation procedures include Taylor linearization. It is always possible to find at least one linear estimator for a total. The total is the key-parameter in sampling theory, most parameters (such as ratios, means, percentages...), being function of unknown totals. Numerical examples are given.

The cross-national epidemiology of panic disorder.

BACKGROUND: Epidemiological data on panic disorder from community studies from 10 countries around the world are presented to determine the consistency of findings across diverse cultures. METHOD: Data from independently conducted community surveys from 10 countries (the United States, Canada, Puerto Rico, France, West Germany, Italy, Lebanon, Taiwan, Korea, and New Zealand), using the Diagnostic Interview Schedule and DSM-III criteria and including over 40,000 subjects, were analyzed with appropriate standardization for age and sex differences among subjects from different countries. RESULTS: The lifetime prevalence rates for panic disorder ranged from 1.4 per 100 in Edmonton, Alberta, to 2.9 per 100 in Florence, Italy, with the exception of that in Taiwan, 0.4 per 100, where rates for most psychiatric disorders are low. Mean age at first onset was usually in early to middle adulthood. The rates were higher in female than male subjects in all countries. Panic disorder was associated with an increased risk of agoraphobia and major depression in all countries. CONCLUSIONS: Panic disorder is relatively consistent, with a few exceptions, in rates and patterns across different countries. It is unclear why the rates of panic and other psychiatric disorders are lower in Taiwan.

Estimating means and percentages in a complex sampling survey: application to a French national survey on sexual behaviour (ACSF). Analyse des Comportements Sexuels en France.

Two-phase stratification sampling with unequal selection probabilities is a relatively cost-efficient strategy to address problems on a nationwide basis and to perform comparative analyses of specific subgroups. This was the case with the ACSF survey. Specific procedures to estimate the variances of unbiased estimators in complex sampling designs are not included in standard statistical packages and no specialized software is available for two-phase sampling. A detailed synthesis of general basic rules for inference about a target population from a probability sample is first presented. We follow with a standard procedure to estimate means and percentages with their confidence intervals according to the design. Finally, numerical results are discussed.

Handedness scale: how many and which items?

A stepwise analysis of the Cronbach Alpha Coefficient (CAC) was performed on five large samples of adults and young children, in order to choose the ''minimum'' set of items of a handedness scale which gives the maximum reliability. In adults, a handedness scale with 12 items has nearly the same or even a better CAC than other scales with more items; so, a choice of 10 to 12 items seems to be adequate. For children, a scale with eight items seems to be quite reliable but it is not impossible that a scale including more items would lead to a slight increase of CAC. The controversial usefulness of a precise assessment of the ''general handedness factor'' (the first principal component) generated by handedness questionnaires and its J-shaped distribution in the general population are discussed.

A regression survival model for testing the proportional hazards hypothesis.

A semi-parametric generalization of the proportional hazards regression model is defined, whereby the hazard functions can cross for different values of the covariates. In the two-sample comparison, it includes in particular the case of two Weibull distributions differing in scale and shape parameters. A global test of the proportional hazards assumption is proposed against such defined alternatives. Its power in the two-sample case is compared to that of previously described tests by using simulation experiments. Survival data of patients with breast carcinoma, including several prognostic factors, are presented as an illustration.

Cross-national epidemiology of major depression and bipolar disorder.

OBJECTIVE: To estimate the rates and patterns of major depression and bipolar disorder based on cross-national epidemiologic surveys. DESIGN AND SETTING: Population-based epidemiologic studies using similar methods from 10 countries: the United States, Canada, Puerto Rico, France, West Germany, Italy, Lebanon, Taiwan, Korea, and New Zealand. PARTICIPANTS: Approximately 38000 community subjects. OUTCOME MEASURES: Rates, demographics, and age at onset of major depression and bipolar disorder. Symptom profiles, comorbidity, and marital status with major depression. RESULTS: The lifetime rates for major depression vary widely across countries, ranging from 1.5 cases per 100 adults in the sample in Taiwan to 19.0 cases per 100 adults in Beirut. The annual rates ranged from 0.8 cases per 100 adults in Taiwan to 5.8 cases per 100 adults in New Zealand. The mean age at onset shows less variation (range, 24.8-34.8 years). In every country, the rates of major depression were higher for women than men. By contrast, the lifetime rates of bipolar disorder are more consistent across countries (0.3/100 in Taiwan to 1.5/100 in New Zealand); the sex ratios are nearly equal; and the age at first onset is earlier (average, 6 years) than the onset of major depression. Insomnia and loss of energy occurred in most persons with major depression at each site. Persons with major depression were also at increased risk for comorbidity with substance abuse and anxiety disorders at all sites. Persons who were separated or divorced had significantly higher rates of major depression than married persons in most of the countries, and the risk was somewhat greater for divorced or separated men than women in most countries. CONCLUSIONS: There are striking similarities across countries in patterns of major depression and of bipolar disorder. The differences in rates for major depression across countries suggest that cultural differences or different risk factors affect the expression of the disorder.

Case counting in epidemiology: limitations of methods based on multiple data sources.

BACKGROUND: The application of capture-recapture methods in epidemiology has been proposed as an alternative to field surveys. This methodology is important for the future of epidemiology and deserves a critical analysis. METHODS: This paper reviews conditions for applying the capture-recapture models to epidemiological data, taking into account practical considerations, in particular the problem of case definition. RESULTS: The underlying assumptions are particularly restrictive resulting in a theoretical limitation of their applicability. In spite of the statistical developments designed to overcome these difficulties, the practical conditions for using the existing lists are often not fulfilled (availability, confidentiality). The major restriction is on the quality of the data which are often far below the standards required in specific prevalence surveys and which may differ between lists. This may result in a dramatic lack of specificity. The definition of the virtual subgroup of patients missing in all lists as generated by the statistical procedure, is questionable particularly when counting living patients. Field studies would be necessary for validation. CONCLUSIONS: In some particular situations (e.g. deceased patients, rare diseases), this methodology may provide a useful approximation to the number of ill subjects events, but users should be aware of their poor specificity. It can also be useful to complement data from surveillance systems by careful cross-checking with independent sources of information. Currently, this method cannot, in any way, replace direct population prevalence or incidence surveys.

Classification and epidemiology of social phobia.

The individualization of social phobia among other phobic disorders is very recent, although previous clinical descriptions can be found in the literature. The new classifications (DSM-III, DSM-IV and ICD-10) have provided operationalized criteria for this disorder, which have allowed researchers to conduct epidemiological studies. However, some diagnostic issues are not completely solved, namely, those with other boundary disorders. Cross-cultural prevalence and risk factors of social phobia are reviewed. Results of a French community study have found a lifetime prevalence rate of 2.1% in males and 5.4% in females. Comorbidity of social phobia with other anxiety disorders and major depression was high. Suicidal tendencies, family history and health services utilization were analyzed according to the lifetime comorbidity pattern of social phobia and depression.