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Biomedical subjects

M Chavance

Publications and source records attributed to M Chavance.

At least 19 recordsLinked to original sources
PubMed1995

HIV/HTLV-I coinfection and clinical grade at diagnosis.

A total of 963 HIV-infected patients have been identified or followed up in Martinique since 1985. Medical files were used to retrieve information about age, sex, circumstances of diagnosis, HTLV-I status, and HIV clinical grade at first examination according to CDC criteria from 1987. Complete information was available for 774 patients. At the first clinical examination, the clinical grade of 65 coinfected patients was more severe than that of the monoinfected patients (GIV versus GII, OR = 2.60, p < 0.01), but after adjustment for age and sex, this odds ratio was reduced 1.57. Although this study cannot invalidate the hypothesis of a faster progression toward AIDS of coinfected than of monoinfected patients, it shows that one or several other mechanisms contribute to the different grades of severity at the first clinical examination observed between these two categories of patients. We believe that HTLV-I infection acquired during adulthood is a marker of high-risk behavior and that it might be associated with early or multiple HIV infections.

Adult↗
PubMed1993

Smoking, CD45R0+ (memory), and CD45RA+ (naive) CD4+ T cells.

The relationship between smoking and percentages and counts of T-cell subsets, in particular CD45R0+ (memory) and CD45RA+ (naive) CD4+ lymphocytes, have been assessed in a sample of 311 middle-aged men working in the Paris area. Percentages of lymphocytes with the phenotypes CD4+, CD8+, CD4+CD45R0+, and CD4+CD45RA+ were determined using double immunofluorescence labeling. All cell counts, including CD4+CD45R0+, and CD4+CD45RA+ lymphocytes increased significantly with tobacco consumption, as did the percentages of lymphocytes with the CD4+CD45R0+ and CD4+ phenotypes. The increase in the percentage of lymphocytes with the CD4+CD45RA+ phenotype, although not significant, was similar to that observed in the percentage of CD4+CD45R0+ lymphocytes. When the proportions of CD4+ cells with the CD45R0+ or the CD45RA+ phenotype were considered, no specific modification of any of these two sub-populations was observed: the effect of smoking on memory and naive Cd4+ lymphocytes seemed to be equivalent.

Adult↗
PubMed1993

Does multivitamin supplementation prevent infections in healthy elderly subjects? A controlled trial.

We performed a double blind randomized study in order to assess the efficacy of a multivitamin supplement for the prevention of common infections in healthy elderly subjects. Non-institutionalized, independent subjects over 60 years of age, living in the Nevers area (central France) were recruited by announcements and randomly assigned to a treatment or a placebo group. The treatment or placebo tablets were to be taken daily for 4 months. The principal criterion of response was the incidence of infections, as recorded from a detailed questionnaire presented at entrance, in the middle (2 months) and at the end (4 months) of the study. Blood samples were taken at the entrance in the study and after two and four months in order to monitor vitamin status. No significant difference was found between the two groups for the incidence of infections. In fact the observed incidences during the two two-month periods were higher in the treatment (0.38 and 0.21) than in the placebo group (0.29 and 0.13). After two months and after four months of supplementation, blood vitamin indicators of the subjects were significantly higher in the treatment than in the placebo group for vitamins B1, B2, B6, E and folates (p < 0.001). The improvement of the vitamin C status was slightly higher in the treatment than in the placebo group. For vitamin A status, the evolution was similar in the two groups. In conclusion, short-term supplementation of healthy elderly subjects with the investigated supplement is not likely to afford a meaningful protection against common infections.

Aged↗
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↗