Biomedical subjects

C Quantin

Publications and source records attributed to C Quantin.

At least 19 recordsLinked to original sources

PubMed2003

Chromium availability in ultramafic soils from New Caledonia.

The sources and potential availability of chromium (Cr) on soils formed on ultramafic rocks were investigated with mineralogical studies and selective chemical extractions. Soil solutions were collected in the field (i) along a soil toposequence under natural vegetation with ceramic cups; (ii) under grass in a mandarin trees plantation with tension-free tube lysimeters. On selected soil solutions, the Cr(VI) was determined colorimetrically with the s-diphenylcarbazide method and total Cr by ICP-AES and speciation of Cr(VI) was performed with the MINEQL+ V 4.5 software. The main mineralogical sources of Cr were Cr-substituted goethite and chromite. Up to 90 mg kg(-1) of Cr was extracted by KH(2)PO(4), whereas KCl extractable Cr was very low, indicating that exchangeable Cr was mainly in the highly toxic Cr(VI) form in these soils. Under natural vegetation, the Cr concentrations in the soil solutions remained relatively low (<20 microg l(-1)) due to the high retention of the Cr(VI) anions by Fe-oxides. The Cr concentrations were larger in well aerated colluvial soils, where high levels of Mn-oxides are able to oxidize Cr(III) to Cr(VI), than in piedmont soil where the Mn-oxide content is lower, or in alluvial soils from the lowlands, where waterlogging occurs. Cr concentrations reached 700 microg l(-1) in the field that was fertilized with high amount of phosphorus, due to the exchange of Cr(VI) with phosphate. In such conditions, toxicity phenomena for crops can be expected.

Biological Availability↗

PubMed2003

Law and standards faced to market rules in health information security.

This paper presents the main differences existing in the elaboration process of law and standard and analyses their potential conflicts. It also describes the respective force of law and standards in three main areas: legal threat versus financial threat, conflict versus cooperation and finally their respective position faced to oligarchic power.

Compensation and Redress↗

PubMed2003

A methodology for multi-source Record Linkage.

As patient's medical data is disseminated in different health structures, building a data-warehousing system at a regional level, for healthcare co-operation, has some specific requirements compared to intra healthcare structure data-warehousing projects. In particular, there is no common patient electronic record's identifier among all the sources. Hence, data integration and Record Linkage is the most important issue in such projects. In this paper, we present Background on Information integration with the two main approaches of the problem: Schema Integration approach and Entity reconciliation approach. We show the limits of each of the two approaches and propose an approach based on theory of a set partitioning and instance identification.

Computer Systems↗

PubMed2002

[Evaluation of prevention strategies for congenital toxoplasmosis: a critical review of medico-economic studies].

BACKGROUND: Congenital toxoplasmosis (CT) may lead to serious neurological or sensory consequences. A serological screening of women at risk of acquiring toxoplasmosis became mandatory in France, first during the visit before wedding (1978), then during the visit for pregnancy declaration (1985) and at last with a monthly follow-up during pregnancy since 1992. The efficacy and the profitability of the program was never assessed, in spite of the modification of the epidemiological context. However medico-economical studies were conducted in countries in which no prevention program for CT was available to determine the interest of an antenatal screening similar to the French one or of other prevention strategies. METHODS: Eight studies comparing at least two strategies were selected. Methodologies used in those studies were analyzed by two independent readers with the help of a standardized scale. A score was calculated for each study. RESULTS: Each study analyzed suffered from methodological limitations, in particular concerning the estimation of antenatal treatment efficacy, which could lead to invalidate their conclusion. The most reliable studies in regard to methodological guidelines, that is with the higher score, concluded that antenatal screening was not contributive. However, they could not be transposed directly in the present French situation, because of the difference of the epidemiological and economical context. CONCLUSIONS: Given the difficulty to obtain a clear conclusion, it seems necessary to perform a rigorous decision analysis to identify the more effective and acceptable program in terms of human and financial costs for preventing congenital toxoplasmosis.

Cost-Benefit Analysis↗

PubMed2002

[A diagnostic strategy for isolated pulmonary nodules less than 2 cm in diameter].

The object of this study is to determine the best diagnostic strategy for isolated pulmonary nodules less than 2 cm in diameter starting from decision analysis. The diagnostic pathway included strategies: 1. Observation with a thoracic tomodensitometry (TDM) every 3 months. 2. Percutaneous needle biopsy. 3. Video-assisted thoracoscopic surgery (VATS) resection. 4. Resection by thoracotomy. Observation was the best strategy for non-smokers in their 40's with a cost of 57-69 Francs per year of life gained. Needle biopsy was the best strategy for a 1 cm nodule in patients of 50 years, smokers and non-smokers (life expectancy 29.38 and 24.44 years). The best strategy for a 2 cm nodule was needle biopsy in 40 year old smokers (life expectancy 34.18 years) and in non-smokers aged 50-60 years with a life expectancy from 20.0 to 28.2 years. VATS was the best strategy for a 1 cm nodule in smokers over the age of 60 for a 2 cm nodule over the age of 50. The costs were 1 811, 3 214, 1 873, 1 811 and 6 093 Francs respectively per year of life gained. During the sensitivity analysis VATS remained the best strategy provided the post-operative mortality remained below 2%. When the risk of malignancy is only moderate needle biopsy may be recommended but when the risk of malignancy is high it is preferable to advise VATS as the method of diagnosis.

Adult↗

PubMed2002

Assessing time-by-covariate interactions in relative survival models using restrictive cubic spline functions.

BACKGROUND: The Cox model is widely used in the evaluation of prognostic factors in clinical research. However, in population-based studies, which assess long-term survival of unselected populations, relative-survival models are often considered more appropriate. In both approaches, the validity of proportional hazards hypothesis should be evaluated. METHODS: We propose a new method in which restricted cubic spline functions are employed to model time-by-covariate interactions in relative survival analyses. The method allows investigation of the shape of possible dependence of the covariate effect on time without having to specify a particular functional form. Restricted cubic spline functions allow graphing of such time-by-covariate interactions, to test formally the proportional hazards assumption, and also to test the linearity of the time-by-covariate interaction. RESULTS: Application of our new method to assess mortality in colon cancer provides strong evidence against the proportional hazards hypothesis, which is rejected for all prognostic factors. The results corroborate previous analyses of similar data-sets, suggesting the importance of both modelling of non-proportional hazards and relative survival approach. We also demonstrate the advantages of using restricted cubic spline functions for modelling non-proportional hazards in relative-survival analysis. The results provide new insights in the estimated impact of older age and of period of diagnosis. DISCUSSION: Using restricted cubic splines in a relative survival model allows the representation of both simple and complex patterns of changes in relative risks over time, with a single parsimonious model without a priori assumptions about the functional form of these changes.

Aged↗

PubMed2001

[Medico-economic impact of the Program of Medicalization of the Information System on hospital stay for myocardial infarction: influence of the quality of data collection and hospitalization length].

The aim of the Medicalisation Program of the Information System was to describe the activity of hospital for budget allocation. This work concerned the whole hospitalizations in the unit of intensive care of cardiology of Dijon for a myocardial infarction (MI) during the 1st half of 1998 (59 patients). The objectives of this study were: 1) the estimate of the real cost of MI management; 2) the comparison of this cost with the reference cost, determined from the data of the National Basis of Costs (BNC); 3) the economic impact of the quality of coding. The real global cost of MI was estimated at 2,323,542 FF (average by patient: 39,382 +/- 15,718 FF). Sixty eight per cent of the costs are directly related to the standing fixed overheads; in contrast, the medical and the therapeutic acts accounted for only 32% of the estimated real cost. A 52% over-estimation was highlighted between the estimated real cost and the cost of reference (p < 0.001). The errors of coding accounted for an under-estimation of only 3.6% of the cost of reference. The duration of hospitalization was significantly higher than the stay length taken from the national reference database (12.9 +/- 5.4 versus 9.2 +/- 2.1 days; p < 0.001), and was mainly responsible for these discrepancies of costs.

Costs and Cost Analysis↗

PubMed2001

Modelling time-dependent hazard ratios in relative survival: application to colon cancer.

The Cox model is widely used in the evaluation of prognostic factors in clinical research. In population-based studies, however, which assess long-term survival of unselected populations, relative survival models are often considered more appropriate. In both approaches, the validity of proportional hazard hypothesis should be evaluated. To explore the validity of the proportional hazard assumption in a population-based study of colon cancer, to propose non-proportional hazard relative survival models and to evaluate their utility. The use of a piecewise proportional hazard relative survival model in colon cancer has shown that the effects of most clinical prognostic factors such as age, period of diagnosis and stage are non-proportional. The non-proportional hazard relative survival models developed in this article have been found to be efficient tools for better understanding the time-dependent aspect of prognostic factors.

Aged↗

PubMed2001

An approach for integrating heterogeneous information sources in a medical data warehouse.

In recent years, medical professionals are witnessing an explosive growth in data collected by various organizations and institutions. At the same time, the ongoing developments of networking technologies provide doctor with the capability to access these data across the boundaries of interconnected computers. In this paper we present a medical data warehousing methodology that aims to use data semantics to regroup and merge patients' medical data from different health information systems, which may be autonomous and heterogeneous. The proposed solution takes into account European laws concerning the security and anonymity of personal data.

Database Management Systems↗

PubMed2001

Quality assessment of cervical screening: a population-based case-control study in the C te-D'Or region, France.

Our objectives were to evaluate the effectiveness of cervical cancer screening outside organized programs in the prevention of cervical carcinoma in situ (CIS) and to enhance the way in which case control studies avoid some common biases. In our case-control study, we assessed all incident, histologically verified cases of CIS registered from 1987 to 1997 in the population-based cancer registry of C te-d'Or, France (N = 104) and 208 controls randomly selected from the screened population and matched for age, date of last screening, residence, and pathology laboratory results. We considered as appropriate for controls screened women who had had at least one Papanicolaou smear in the 3 years preceding the diagnosis or similar period. Screening for controls was higher (67.8%) than for cases (41.4%; P < .001), with a relative protection against CIS of 3.09 (95% confidence interval, 1.83-5.22) and a prevented fraction in the screened population of 45% to 50%. These findings suggest a protective advantage for CIS even in the absence of organized screening. The methodologic approach has advantages as compared to previous types of case-control studies. Although further refinements still are warranted, learning about the protective effect of screening for CIS provides information that may be useful in assessing the impact of a screening policy on women actually at risk of invasive cervical cancer.

Carcinoma in Situ↗

PubMed2001

A virtual intranet and data-warehousing for healthcare co-operation.

As patient's medical data is disseminated in different health structures, developing a medical or epidemiological patient-oriented data warehouse has some specific requirements compared to intra healthcare structure data-warehousing projects. The difference is that the healthcare structures implicated in a patient-oriented data warehouse project require some considerations about the confidentiality of the patient data and of the activities of healthcare structures. Building a data-warehousing system at a regional level, for example in cancerology, requires the participation of all concerned health structures, as well as different health professionals. The heterogeneity of sources medical data of has to be taken into account for choosing between several organizational configurations of the data warehousing system. In top of data warehousing, we propose a concept of Virtual Intranet, which provides a solution to the problem of medical information security arising from heterogeneous sources.

Computer Communication Networks↗

PubMed2001

The Swiss solution for anonymously chaining patient files.

Being able to link the successive hospitalizations of a given patient for epidemiological surveys together by preserving patient anonymity requires a specific procedure. For its medical hospital statistics, Switzerland has adopted anonymous record linkage procedure, ensuring an irreversible transformation of identity and allowing the linkage of anonymous files. Concepts, algorithms and organization have been developed by the Federal Statistical Office. Algorithms are closed to those developed in Dijon University Hospital.

Algorithms↗

PubMed2001

[Using discharge abstracts as a tool to assess a regional perinatal network].

To assess the regional perinatal network of Burgundy (20 obstetrical units; 18,000 births/year), discharge abstracts are collected for all mothers and all neonates. Discharge abstracts are expanded with some additional data. According to the French law, data are rendered anonymous in each hospital before their transmission to the teaching hospital for statistical analysis. The linkage of all anonymous information concerning a patient is obtained. Moreover, this specific procedure allows the linkage of data concerning each mother and her corresponding neonate. This study shows that after an expanded data quality control, the linkage between data of the mothers and their infants is obtained in 99.8% of births.

Adult↗

PubMed2000

Anonymous statistical methods versus cryptographic methods in epidemiology.

Sensitive data are most often indirectly identifiable and so need to be rendered anonymous in order to ensure privacy. Statistical methods to provide anonymity require data perturbation and so generate data processing difficulties. Encryption methods, while preserving confidentiality, do not require data modification.

Journal Article↗

PubMed2000

[Security services: an overview of the French legislation on cryptography].

This paper deals with the main security services of data protection: integrity, authentication, nonrepudiation and confidentiality. It describes the different tools which may be used to achieve these security objectives: encryption, digital signature, access controls, integrity control, audit and certification. The French legislation concerning encryption has been recently updated in order to simplify the use of encryption techniques for personal data security. This legislation describes different authorization or reporting procedures according to the type of the request (application, equipment, import or export of encryption techniques) and the security level required.

Algorithms↗

PubMed2000

[Security of healthcare data networks used for epidemiological studies].

Record linkage, for compiling sameperson records from various source files, can improve the feasibility of epidemiological research using populationbased studies. The question is comply with the European legislation on data privacy and data security. For example, a computerized record hash coding and linkage procedure is described to link medical information within the framework of epidemiological followup. Before their extraction, files are rendered anonymous using a oneway hash coding based on the standard hash algorithm (SHA) function. Once rendered anonymous using the software ANONYMAT, the linkage of patient information can be accomplished by means of a mixture model, taking into account several identification variables. An application of this anonymous record linkage procedure was carried out in order to link medical files on cancer, from 3 hospitals of the French RhôneAlpes region. This application stresses how the use of the ANONYMAT software allows compliance with the legislation on data confidentiality without entailing problems on data availability.

Computer Communication Networks↗

PubMed2000

Anonymous statistical methods versus cryptographic methods in epidemiology.

Computer Security↗

PubMed1999

Variation over time of the effects of prognostic factors in a population-based study of colon cancer: comparison of statistical models.

The authors compare the performance of different regression models for censored survival data in modeling the impact of prognostic factors on all-cause mortality in colon cancer. The data were for 1,951 patients, who were diagnosed in 1977-1991, recorded by the Registry of Digestive Tumors of Côte d'Or, France, and followed for up to 15 years. Models include the Cox proportional hazards model and its three generalizations that allow for hazard ratio to change over time: 1) the piecewise model where hazard ratio is a step function; 2) the model with interaction between a predictor and a parametric function of time; and 3) the non-parametric regression spline model. Results illustrate the importance of accounting for non-proportionality of hazards, and some advantages of flexible non-parametric modeling of time-dependent effects. The authors provide empirical evidence for the dependence of the results of piecewise and parametric models on arbitrary a priori choices, regarding the number of time intervals and specific parametric function, which may lead to biased estimates and low statistical power. The authors demonstrate that a single, a priori selected spline model recovers a variety of patterns of changes in hazard ratio and fits better than other models, especially when the changes are non-monotonic, as in the case of cancer stages.

Aged↗