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PubMed1992

A review of epidemiological methods applied in studies on laboratory animal allergy. With a discussion of the relation between prevalence and risk of an irreversible disease in a dynamic population of constant size.

The risk of developing an occupational allergic respiratory disease depends strongly on the duration of exposure. For estimating the instantaneous risk (hazard function) in a dynamic cohort, information is required for each cohort member on the time of exposure either until disease onset or until termination by leaving the job or the end of the study. However, most existing epidemiological studies on occupational allergies are cross-sectional, computing prevalences; no information on job-leavers and on their disease status is obtained. The functional dependency of prevalence on risk, as well as on the rate of leaving the job among the diseased and on the distribution of exposure duration, is described, with special attention to the sensitivity of the prevalence to differences of the rate of leaving the job. A literature review of 15 studies on laboratory animal allergy is given; none of the studies collected and reported all the information necessary for risk estimation.

Animals↗
PubMed1975

Evaluation of a measles-smallpox vaccination campaign by a sero-epidemiologic method.

An assessment technique has been devised whereby children from 30 randomly chosen sampling sites are visited within three days of measles-smallpox vaccination and one month later. Vaccination coverage is measured at house visits and immunologic status is determined by collection of early and late blood samples on filter papers from substratified children in priority age-groups, and by looking at vaccination scars. The methodology was employed in a rural area of the Ivory Coast during the maintenance phase of a measles-smallpox vaccination program; 1762 children from 0--72 months old were inspected. Children in the target age groups, 6--24 months, had a vaccination coverage of 53.6% whereas children outside of the target group had a 10.5% coverage. Of 571 target age children, 94.6% had a measles hemagglutination-inhibition antibody titer of less than 1:10 dilution at the first visit, and were presumed susceptible to measles or vaccine. Of 247 substratified children 6--8 months, 98.3% were susceptible to measles before vaccination; 84.3% of 127 vaccinated children in this age-group sero-converted when re-tested. Of 324 children 9--24 months, 91.7% were susceptible before the campaign; 94.7% of 170 vaccinated children in this age-group converted. A positive history of prior measles or prior measles-vaccination was not a good indicator of measles serologic status. The smallpox vaccination major reaction rate was 93.2%; 91.4% of children with a recent vaccination scar sero-converted to measles vaccine. Thus, the smallpox scar read at the second visit proved the best clinical marker for determining both coverage and immunologic effectiveness of the campaign.

Age Factors↗
PubMed1991

Parkinson's disease: an epidemiologic method for distinguishing between symptomatic and neuroprotective treatments.

Recent studies have suggested that deprenyl may exert a neuroprotective influence and thus retard progression of Parkinson's disease (PD). On the other hand, the data do not disprove that deprenyl is primarily another form of symptomatic therapy like levodopa. Longitudinal Gompertzian analysis demonstrates the absence of beneficial alteration of intrinsic or environmental influences on the epidemiology of PD mortality after the introduction of levodopa. Moreover, this method demonstrates the basis for the enhanced survival in PD that resulted from the efficacy of levodopa as symptomatic therapy. If deprenyl becomes standard therapy in PD and exerts a beneficial (neuroprotective) influence on intrinsic and environmental pathogenic mechanisms, this will become evident by a decrease in the PD mortality rate in the United States in men at age 73.4 years and in women at age 79.1 years. The ability to accurately assess the overall impact of new therapies on the general population is increasingly important in an era of upward spiraling health care costs. Longitudinal Gompertzian analysis is a simple method of detecting and distinguishing between symptomatic (competitive) and protective (intrinsic and environmental) influences on disease mortality at the population level after the introduction of new therapies.

Aged↗
PubMed1976

Is Hodgkin's disease infectious? Discussion of an epidemiologic method used to impute that it is.

A method proposed by MacMahon for the differentiation between familial and environmental causes for disease has recently been applied to demonstrate an environmental etiology for Hodgkin's disease. It is shown that the method, which depends on the comparison of time-of-onset differences with age-at-onset differences for familial pairs with disease, is biased toward results suggestive of an environmental etiology when applied to data of the kind typically analyzed--data restricted to instances in which both members of a familial pair develop disease in a specified, limited time interval. Other features of such data are discussed.

Age Factors↗
PubMed1990

Epidemiological methods to study the interaction between HIV infection and other sexually transmitted diseases.

Numerous studies performed over the past 5 years have indicated an association between HIV infection and other sexually transmitted diseases (STDs), particularly those involving genital ulceration. Such an association may be causal, indicating that STDs increase susceptibility to, or infectivity of, HIV infection or may result, in whole or in part, from the mutual dependence of HIV and STDs on patterns of sexual activity, or from an effect of HIV infection on the clinical course of STDs. In this paper we discuss the issues arising in the design and analysis of studies conducted to investigate this association. A numerical illustration is used to demonstrate non-causal associations that may arise in observational studies due to confounding and misclassification. Published cross-sectional and longitudinal studies are reviewed, and recommendations made for future studies. Special emphasis is given to the use of randomized intervention trials to overcome many of the biases associated with observational studies, and to provide information on the efficacy of intensive STD treatment programmes in reducing the transmission of HIV.

Cross-Sectional Studies↗
PubMed1991

Development of epidemiological method for the Helicobacter pylori by polymerase chain reaction.

The polymerase chain reaction was used to develop a method for the detection of Helicobacter pylori, a causative agent of gastritis, as well as for the elucidation of its mode of transmission. A genomic library of Helicobacter pylori DNA in Escherichia coli JM109 was constructed by cloning Hind III-digested DNA fragments into plasmid vector pUC18. The nucleotide sequences from seven recombinant clones were determined and five sets of oligonucleotide primers were synthesized on the basis of the sequences from five clones (B4, B9, B10, C15 and I22). The PCR amplifications with these primers were performed using DNA samples from five strains of Helicobacter pylori, two Campylobacter spp. and eleven species of enteric bacteria. Amplifications of the target DNA fragments in all of 5 strains of Helicobacter pylori were observed from the PCR with primers derived from clone B4, B9, C15 and I22. When the specificity was checked with the DNA samples from 13 other bacteria as template DNA for the PCR, specific amplification that produced the correct size of the target DNA of Helicobacter pylori was shown only in the PCR with primers derived from clone B9 and C15. The detection limit in the PCR amplification, determined by the heat-lysis method, was 500 cells of Helicobacter pylori.

Base Sequence↗
PubMed1979

[Study of 357 cases of phlebitis of the lower extremities in 2 inter-regional samplings. I. Methods, epidemiological data and analysis of etiopathogenetic elements].

Using a specially designed record card, 357 cases of superficial and deep thrombophlebitis and phlebothrombosis of the lower extremities have been investigated. Of these 261 were observed in Piedmont and 96 in the Trentino region. A comparative study of aetiopathogenetic data in the two regions was made possible by means of punched cards and subsequent computer processing. The study was completed by statistical analysis. Apart from the region of birth and residence, sex (prevalently female) and age which in both samples mainly affects subjects aged between 30 and 45, the type of working activity was considered in relation to sex and age, frequency of absenteeism (higher in Piedmont), family history of venous disease, incidence of orthostatism, the use of contraceptive pills, the period in which the first clinical signs occurred with considerable diversity between the two regions, traumas (more frequent in Piedmont) and the incidence of the different causes which was vastly different in the two samples, were assessed. On the basis of the comparative data obtained, an interpretation of the real significance of the results is attempted, reference also being made to the type of population under examination, the Piedmontese being considered of mixed strain and the Trentino pure.

Adolescent↗