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Biomedical subjects

C Quantin

Publications and source records attributed to C Quantin.

46 records · Page 3Linked to original sources
PubMed1996

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.

Antineoplastic Agents↗
PubMed1996

Extraction and anonymity protocol of medical file.

To carry out the epidemiological study of patients suffering from a given cancer, the Department of Medical Informatics (DIM) has to link information coming from different hospitals and medical laboratories in the Burgundy region. Demands from the French department for computerized information security (Commission Nationale de l'Informatique et des Libertés: CNIL), in regard to abiding by the law of January 6, 1978, completed by the law of July 1st, 1994 on nominal data processing in the framework of medical research have to be taken into account. Notably, the CNIL advised to render anonymous patient identities before the extraction of each establishment file. This paper describes a recently implemented protocol, registered with the French department for computerized information security (Service Central de la Sécurité des Systèmes d'information : SCSSI) whose purpose is to render anonymous medical files in view of their extraction. Once rendered anonymous, these files will be exportable so as to be merged with other files and used in a framework of epidemiological studies. Therefore, this protocol uses the Standard Hash Algorithm (SHA) which allows the replacement of identities by their imprints while ensuring a minimal collision rate in order to allow a correct linkage of the different information concerning the same patient. A first evaluation of the extraction and anonymity software with regard to the purpose of an epidemiological survey is described here. In this paper, we also show how it would be possible to implement this system by means of the Internet communication network.

Computer Communication Networks↗
PubMed1995

Structural and conjunctural compensation method for hospital budgetary allocation on the basis of DRGs.

We propose here a structural and conjunctural compensation method to improve budgetary allocation which could be based on Diagnosis Related Groups. This method consists in the determination of sub-group costs within DRGs. The specification of these sub-groups is possible by introducing clinical and social parameters in the statistical model. Hospitals could then compare their sub-group proportions and analyze their differences in relation to conjunctural factors (recruitment, medical practices) and structural factors (technical team, local medical structure). This method also allows an identification of specialty hospitals (outliers) and a compensation allocation for budgeting for these hospitals.

Budgets↗
PubMed1995

A one way public key cryptosystem for the linkage of nominal files in epidemiological studies.

An encryption method is proposed for nominal files to allow their linkage while respecting confidentiality rules. In contrast to most encryption algorithms, this encryption method must be non-reversible. The method is based on congruence, like the SAN MARCO algorithm, and satisfies the two following conditions. 1) Non-reversible enciphering, which implies the possibility of collisions. 2) The collision rate must be minimized, to allow file linkage. The security of this method is, in addition, guaranteed by a key, which is destroyed after enciphering and is not given to the recipient of the coded file.

Algorithms↗
PubMed1992

A model for quality assessment in cervical cytology used as a screening test.

Although many reliability studies on cervical cytology have been carried out, measurements of sensitivity and specificity have rarely been made since biopsies are not often performed on patients with a negative smear result. This screening assessment was performed over 3 years, using a database of 230,167 smears from 177,051 women. It would seem that cervical cytology has a high specificity (over 99%) but a relatively low sensitivity (61%). Values for sensitivity (exceeding 95%) and specificity (exceeding 99%) for invasive carcinoma should be regarded as reasonably accurate as all incident cases of symptomatic cervical carcinoma are recorded in the Burgundy register. The sensitivity (57%) for pre-invasive lesions is underestimated while their prevalence is overestimated: the lack of organized screening leads to the loss of prevalent cases. The predictive value of a positive smear is 76% for moderate-severe dysplasia, 85% for in situ carcinoma and over 95% for invasive carcinoma.

Adolescent↗
PubMed1991

[Prognostic factors in hemorrhagic cerebrovascular accidents in a population register].

Since 1985, cases of acute vascular cerebral diseases observed among the inhabitants of the city of Dijon have been systematically recorded: 88 cerebral haemorrhages were reported from 1985 to 1988. Twenty-five variables have been defined from antecedents, clinical and para-clinical data. Seven variables, were statistically associated with death at the end of the first month: age, severity of neurological palsy, meningeal syndrome, coma or comatose state, hyperglycemia and mass effect on CAT-scan. Using a step-down variable selection procedure, two prognostic factors were found: loss of consciousness and advanced age.

Adult↗
PubMed1990

[The Cox model: limitations and extensions].

The proportional hazards model (Cox's model) does not fit the data in many situations. Its limits are reviewed, together with the main goodness-of-fit techniques. Some possibilities of extending the proportional hazards analysis are also described.

Clinical Trials as Topic↗
PubMedDate not supplied

Irreversible encryption method by generation of polynomials.

Patient follow up, within the framework of epidemiological studies, poses the problem of linking nominal files. An encryption method of identity is proposed to allow the linkage of medical information on the same patient while respecting the confidentiality of medical data. In contrast with most encryption algorithms, the proposed method is mathematically irreversible in response to the requirement of the French National Commission of Computerized Information Security which demands that the cryptosystem must not be decipherable even by the legitimate recipient. In order to prevent deciphering by frequency analysis, the proposed method introduces polynomial operations so that neither indication concerning the length of the string nor a possible repetition of characters can be obtained by code disclosure. The security of the system is reinforced by the use of two keys, the first one to be defined by the producers of information and the second one by the recipient so that nobody can decrypt the enciphered text.

Algorithms↗
PubMedDate not supplied

Influence of obesity and hypertriglyceridaemia on the low HDL2-cholesterol level and on its relationship with prevalence of atherosclerosis in type 2 diabetes.

High density lipoprotein subfraction 2 (HDL1)-cholesterol level is usually decreased in Type 2 (non-insulin-dependent) diabetes. A study was carried out in 251 Type 2 diabetic patients (106 males [M], 145 females [F]) and in 120 non diabetic controls in order to determine the influence of hypertriglyceridaemia and obesity on the HDL2-cholesterol level and to analyse the relationship between HDL2-cholesterol level and atherosclerosis (coronary heart disease, peripheral atherosclerosis or cerebral vascular disease), in Type 2 diabetes. Influence of hypertriglyceridaemia and obesity on HDL2-cholesterol level was studied by comparing the mean values of HDL2-cholesterol between diabetics and controls, after controlling for hypertriglyceridaemia and obesity, and by a multiple linear regression test. A stepwise logistic regression was performed to analyse the association between the prevalence of atherosclerosis and several variables: age, duration of diabetes, hypertension, cigarette smoking, body mass index, mean glycaemia, total cholesterol, triglyceride, HDL-cholesterol, HDL2-cholesterol and HDL3-cholesterol levels. In both men and women, when both of the factors (hypertriglyceridaemia and obesity) were present of when only one was, HDL2-cholesterol level was significantly lower in the diabetic population, compared with controls. But when obesity and hypertriglyceridaemia were absent, HDL2-cholesterol level, in the diabetic population, was not significantly different from controls (M: 17.9 +/- 13.3 vs 20.5 +/- 13.8 mg/dl: NS; F: 30.1 +/- 21.5 vs 27.6 +/- 14.2 mg/dl: NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗