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Biomedical subjects

M Chavance

Publications and source records attributed to M Chavance.

At least 19 recordsLinked to original sources
PubMed1992

Correlated nondifferential misclassifications of disease and exposure: application to a cross-sectional study of the relation between handedness and immune disorders.

In cross-sectional studies, misclassifications of exposure and of health status may be related. For instance some subjects may tend to overreport both exposure and disease. A misclassification is said to be nondifferential if the sensitivity and the specificity which characterize it do not depend on the true status of the subjects for the other variables. Nondifferential misclassifications of two dichotomic variables may be correlated if the probability of being misclassified for one of them depends on the presence of an error of classification for the second one. Models are presented to estimate the bias induced by correlated nondifferential misclassifications on an odds ratio whose true value is unity. For most usual situations, when the great majority of the subjects are healthy and nonexposed, the influence of overreporting is shown to be larger than that of underreporting. It appears to be relatively easy to find a spurious, but significant, relationship. Real data are analysed to show that the potential consequences of correlated nondifferential misclassifications are not purely theoretical. In a sample of 1676 subjects from the general population we observed significant relations between left-hand shift and various aspects of health status: reporting a history of eczema, experience of a serious health problem in the past, experience of a serious health problem presently, use during the last month of analgesics or of drugs for circulatory problems, or digestion, consultation with a physiotherapist or hospitalization during the last year. These results, as with many similar ones previously reported, are highly suggestive of an information bias. They are less easily explained by biological hypotheses, e.g. Geschwind's theory of cerebral lateralization, than by correlated misclassifications resulting from overreporting of both the use of the left hand and the existence of some health problems by healthy right-handers. The modelling used in this report supports this hypothesis.

Adult↗
PubMed1992

Personal factors related to the perception of occupational exposure: an application of a job exposure matrix.

Whether certain personal characteristics influence the perception of exposure to dusts, gases or fumes was assessed in 6803 men and 6765 women drawn from nonmanual worker households in seven French cities. Factors modifying the strength of the association between two estimates of exposure (here a job exposure matrix estimate and exposure reported by the subjects) are potential recall determinants of exposure. This association was significantly stronger in men than in women, suggesting a better perception of exposure in men. The strength of the association between both estimates of exposure increased significantly among men according to educational level. Smoking habits had no effect on the perception of exposure. The perception of exposure did not vary significantly according to respiratory symptoms in women. In men, subjects without chronic cough or chronic bronchitis had a significantly higher perception of exposure than the others, but no difference was shown for wheezing, dyspnoea or asthma.

Adult↗
PubMed1992

[Jackknife and bootstrap].

The jackknife and the bootstrap are two non parametric methods which provide estimates- of the bias and the variance of an estimator, without any assumption about its statistical distribution. The jackknife is based on the observation of the estimator for subsamples, generally of size n-1, obtained from the original sample. The bootstrap is based on the observation of the estimator on size n samples drawn from the original sample. The two methods are presented, their principle is illustrated through their application to simple examples and to more complex epidemiological problems.

Bias↗
PubMed1991

HTLV-I infection in French West Indies: a case-control study.

A case-control study was performed in Martinique, French West Indies, comparing 66 anti-p24 antibody carriers to 91 seronegative subjects for HTLV-I, matched for age and place of residence. The aim of our study was to identify factors associated with HTLV-I infection and to observe whether clinical examination and biological measurements would reveal any abnormalities among the seropositive subjects. We observed a predominance of females among seropositive subjects (74% compared to 59%, p less than 0.05), and a greater risk due to earlier blood transfusions (p less than 0.001). This survey revealed important differences between cases and controls regarding socioeconomic factors: cases had fewer luxuries or advantages (i.e. bathroom, toilets, refrigerator, telephone, p less than 0.01), were more corpulent (p less than 0.05), and more often widowed, divorced or separated (p less than 0.01) than the controls. Although the differences were not significant, the seropositive donors seemed to be less educated, and were from a lower socioprofessional class than the seronegative donors. With regard to clinical symptoms (infections, adenopathies, splenomegaly, hepatomegaly) and biological parameters (blood count; T-cell subsets, electrophoresis of protids, immunoglobulins, calcemia, antischistosomal antibody), seropositive subjects appeared to be healthy; no parameters, except for alpha 1 globulin (p less than 0.05) and monocytes (p less than 0.05), were found to be correlated with seropositivity; but these two parameters remained within their normal ranges. This study confirms blood transfusion as a risk factor. It underscored the importance of socioeconomic factors for seropositivity.

Adult↗
PubMed1991

Delayed-type hypersensitivity and circulating basophils. A population study.

The factors related to delayed-type hypersensitivity (DTH) have been investigated in two samples of elderly non-hospitalized (n = 375) and hospitalized subjects (n = 409). Percent basophils was found to be consistently related to the number of positive responses to seven common antigens in the different samples or subsamples considered. The mean number of responses, after adjustment for age, sex and sample was 1.55 below 0.5% basophils, 1.87 between 0.5 and 1.5% and 1.96 over 1.5% (P less than 0.01). No relation was observed between percent basophils and the mean diameter of the positive responses, suggesting that basophils might be related to the early phase of DTH reactions. As previously reported, the number of positive responses was found to be lower in women than in men and to be inversely related to age.

Age Factors↗
PubMed1990

An epidemiological reconsideration of the Geschwind-Galaburda theory of cerebral lateralization.

To contribute to the Geschwind-Galaburda theory of cerebral lateralization, we examined the relationship of left-handedness to allergic disorders and stuttering, using epidemiological data of two French samples, one of which (N = 9591) is representative of the French male population between 17 and 24 years of age. Results showed a higher frequency of stuttering but not of allergic disorders in left-handers. Extreme right-handedness was observed to be significantly associated with a lower frequency of allergic disorders; response bias might explain such a relationship. Findings were confirmed after allowing for potential confounding factors, such as age and education. In both samples, stuttering and allergic disorders were significantly related.

Adolescent↗
PubMed1990

Handedness, immune disorders and information bias.

In order to investigate the relations between handedness and migraine or immune disorders, we performed a case control study comparing the handedness of patients suffering from systemic lupus erythematosus (SLE), type I diabetes, Graves' disease, or migraine to that of a random sample of controls from the general population. A handedness index was measured from a 10-item questionnaire. No significant difference was observed. But when the controls who denied having ever suffered from migraine or any allergic disease were set apart from those who gave at least one positive answer to the same questions, the former were found more right-handed, i.e. with a lower handedness index than the latter (P less than 0.05) and than the SLE patients (P less than 0.05). More generally, the mean observed handedness index of controls giving a positive answer to any question about their health was found repeatedly higher than that of controls giving a negative answer: this was observed for 27 of the 32 questions. These results are highly suggestive of an information bias, the subjects saying they use the right hand for each of the 10 activities considered in the questionnaire being more likely to deny having suffered from a given disease or used, more or less recently, some drug or medical service. Our conviction is that previous observations dealing with the same topic are also more easily explained by the presence of an information bias than by Geschwind's theory. The implications for the design of further epidemiologic studies are discussed.

Adult↗
PubMed1990

Sex ratio of human T-lymphotropic virus type I infection and blood transfusion.

The prevalence of human T-lymphotropic virus type I (HTLV-I) infection is higher for females than for males. Blood transfusion is a potential confounding factor which might contribute to this high female:male ratio. Two studies were performed in Martinique (French West Indies) to clarify this issue: a case-control survey comparing the experience of previous blood transfusion among 62 HTLV-I-seropositive and 88 HTLV-I-seronegative blood donors, and a retrospective study of the sex of recipients of blood. Blood transfusion was strongly associated with HTLV-I infection (odds ratio = 6.4, p less than 0.001). Females were more often given blood transfusions (57.9 percent, p less than 0.001) and received a higher percentage of blood units (53.5 percent, p less than 0.05) than could be expected from their proportion in the general population (51.6 percent). Thus, the high female:male sex ratio of HTLV-I-infected subjects might be due partially to a sex difference for blood transfusion.

Adult↗
PubMed1989

Anti HTLV-I antibodies and HLA phenotypes in the West Indies.

Sera of supposedly healthy blood donors were screened for the presence of anti HTLV-I p24 antibodies, and HLA typing for A, B, C and DR antigens was performed for 68 seropositive subjects and 92 seronegative controls. HLA phenotypes of the two groups were not significantly different but the level of the antibody response was related to the antigens of the HLA-B (P = 0.02) and -C loci (P = 0.003). Subjects with HLA-B12 or -B21 antigens had lower titres than the others. Subjects with HLA-Cw2 or -Cw7 antigens had higher titres than the others, but only the difference between HLA-B12 positive and negative subjects (P = 0.002) remained significant at the alpha = 0.10 level if the classical, although conservative, Bonferroni procedure was used to correct for the number of comparisons performed.

Adult↗
PubMed1989

Vitamin status, immunity and infections in an elderly population.

The relations between vitamin status and immunological parameters or number of infections have been investigated in self-sufficient healthy individuals aged 60 and over. A total of 411 subjects agreed to participate, but 202 were discarded from the main statistical analysis since they could have had their immune or nutritional status modified by a recent infection, vaccination or drug consumption. Plasma concentrations of retinol, alpha-tocopherol, ascorbic acid and vitamin B6 were determined. Three indices of cellular immunity were measured: percentages of T-cell subsets, lymphoproliferative response to phytohaemaglutinin and delayed-type hypersensitivity to 7 ubiquitous antigens. A questionnaire about past infections was presented. Two results, supported by previous experimental observations, should be underlined. Vitamin B6 status was positively related to percentages of T-cell subsets: the lowest percentages of CD5 and CD4 cells were observed in the low B6 status group (50.6 and 32.6 per cent) and the highest percentages in the high B6 status group (62.0 and 41.0 per cent), with intermediate values in the medium group (57.6 and 39.5 per cent). Vitamin E status was negatively related to the number of past infections: subjects with a high alpha-tocopherol plasma concentration had fewer infections during the last 3 years (1.0) than those with a medium (2.2) or a low (2.3) concentration. In spite of these two observations, cellular immunity did not seem to be strongly related to vitamin status in the supposedly healthy population studied.

Aged↗
PubMed1989

Dietary intake and other determinants of blood vitamins in an elderly population.

The relationships of diet, plasma lipids, age, gender, ponderal index, cigarette and alcohol consumption, drug use and infections to blood concentrations of retinol, beta-carotene, alpha-tocopherol, ascorbic acid and vitamins B1, B2, B6 status were studied among 291 men and women aged 60-82 years. Statistically significant correlations between dietary intake and blood indicator levels were found respectively for beta-carotene, alpha-tocopherol, ascorbic acid, vitamins B2 and B6, but not for retinol and thiamin, when the effects of other parameters were controlled. The main other determinants were cigarette consumption which had a negative effect on status for retinol, beta-carotene, alpha-tocopherol, ascorbic acid and vitamin B2; alcohol consumption for retinol, vitamin B6 (positive effect on status) and beta-carotene (decrease of plasma level); plasma lipids and use of hypolipaemic drugs for fat-soluble vitamins; ponderal index for beta-carotene and vitamin B6; gender and use of antibiotics for ascorbic acid. The apparent relation between gender and level of retinol, beta-carotene, alpha-tocopherol and vitamin B6 status was not any more significant after adjustment for alcohol or cigarette consumption. Tobacco and alcohol appear to be associated factors which should be controlled for in studies investigating relations between these vitamins and diseases influenced by smoking and drinking habits.

Age Factors↗
PubMed1988

Seasonal patterns of circulating basophils.

The seasonal patterns of circulating basophils were investigated in a sample of 33,000 French subjects, aged 20-60 years. Circannual variations (minimum in October, maximum in July) which might be related to pollens were observed. Periods with cold weather (temperature below 0 degrees C) correlated to a temporary rise in basophils.

Adult↗
PubMed1987

Modification of force-interval relations during early adaptation to pressure overload in dogs.

Ventricular function was analyzed in the end-systolic and end-ejection pressure-volume diagrams in seven conscious dogs during acute aortic stenosis (AS) and sustained stenosis (SS) 24 h later. Dogs were previously instrumented with a left ventricular micromanometer and ultrasonic crystals measuring left ventricular major and minor axes and parietal wall thickness. The end-ejection pressure-calculated volume points were significantly shifted to the left during SS as compared with those obtained during AS both during a regular atrial pacing (150 beats/min) and during spontaneous heart rate. Postpacing beats were not different during AS and SS. During AS, end-systolic volume was larger after short intervals (SI) between beats (22.5 +/- 1.6 ml) than after long intervals (LI; 20.8 +/- 1.7 ml) for a smaller end-systolic pressure (P less than 0.001). This difference was minimal during SS. When SS was compared with AS, the end-systolic and end-ejection pressure-volume points were significantly shifted to the left after SI but not after LI. This suggests an acceleration of the restitution process during SS that modifies ventricular force-frequency relations and increases ventricular function as compared with AS, particularly for high heart rates.

Adaptation, Physiological↗
PubMed1986

Thyroxine-binding prealbumin, overnutrition and apolipoprotein A1.

Thyroxine-binding prealbumin (TBPA) seems to be more useful than other biochemical markers for the detection of subclinical protein-energy malnutrition. Accordingly, one can question whether its sensitivity to nutritional supply could be used in healthy populations for the discrimination of groups with low or high energy intakes; if such were the case, could TBPA serve as an index of overnutrition? In order to answer these questions, we measured TBPA circulating levels in three groups of healthy French subjects from a working population, with relatively low, medium or high levels of energy intake. We also observed the correlations of this protein with nutrient intakes and with some biological parameters related to the general nutritional status of the subjects. The observed figures did not support the hypothesis that TBPA could be used to discriminate healthy subjects with relatively low or high energy intake nor as an index of overnutrition. This study disclosed a positive relation of TBPA with alcohol consumption and related parameters such as body mass index or gamma-glutamyl transferase as well as a negative one with alpha 2-globulin and gamma-globulin. Other investigators have found similar results in chronic alcoholics, surgical patients, or patients suffering from severe illnesses such as cancer. Here, the study population consisted of adult men, neither undernourished nor suffering from any severe pathology and who could not be considered excessive drinkers. Positive relations were also observed between TBPA and apolipoprotein A1 and HDL cholesterol levels, which are negatively associated with coronary heart disease risk.

Adult↗