Mathematical models and scientific reality in occurrence rates for disease

Primary health care ICD--a tool for general practice research

The International Classification of Diseases (ICD) has become the only diagnostic classification system of international standard that allows reliable comparisons of epidemiological data between countries, parts of a country, levels of health care systems, or different periods of time. However, for primary health care purposes it is too specific to describe problems relevant to the work of general practitioners (GPs). Tools are thus needed to 'compress' data in primary health care for educational, administrative and research purposes. The objective of this paper was to introduce a diagnosis coding system that can be used in primary health care settings for these purposes. Principal diagnoses, as assessed by medical doctors, were collected from 20,648 patient visits. After primary coding, according to the ICD on a five-digit scale, the diagnoses were grouped into larger entities, which reduced the number of diagnoses to one eighth of the original number. The ten most common original five-digit diagnoses accounted for one quarter of all consultations, whereas the ten most common diagnoses counted for one half of all consultations after compressing the data into new categories. Analysing epidemiological data in the records of primary health care by the ICD offers benefits because of the latter's wide use. These are discussed below.

Roles of epidemiology, pathology, molecular biology, and biomarkers in the investigation of occupational lung cancer

The pathology and molecular biology of lung cancer demonstrate that these tumors evolve through a series of mutations, molecular changes, and corresponding morphologic changes. To elucidate how occupational and environmental factors influence lung cancer histogenesis it is important not only to understand epidemiology and the interactions between etiologic agents but also to integrate information from pathology, biochemistry and molecular biology. This review focuses on the range of techniques currently available for characterizing lung cancer and how their prudent use can be beneficial in the identification of occupational carcinogens. Because many occupational and environmental lung cancers are caused by multiple etiologic agents, the integration of histology with cellular, biochemical and molecular biomarker techniques may provide new approaches for understanding the disease process.

On the terminology and dimensions of incidence

This paper is a review of the concept of incidence and the measures of incidence commonly used. The three components of incidence (observed event, population at risk, and observation period) and the four measures of incidence (incidence as number of events, as number of events per time unit, as number of events per unit of amounts of observation, and as probability) are discussed. The terminology and dimensions of incidence measures used in epidemiology literature are reviewed. Ambiguities and uses of the same term for different purposes seem to suggest the need for standardized terminology. Incidence measures with length-based amount of observation are also briefly discussed.

Nosocomial Infections in Spain: Results of Five Nationwide Serial Prevalence Surveys (EPINE Project, 1990–1994)

Objective: To determine trends in rates of nosocomial infections in Spanish hospitals.

Design: Prospective prevalence studies, performed yearly from 1990 through 1994.

Setting: A convenience sample of acute-care Spanish hospitals.

Participants and Patients: The number of hospitals and patients included were as follows: 1990, 125 hospitals and 38,489 patients; 1991, 136 and 42,185; 1992, 163 and 44,343; 1993, 171 and 46,983; 1994, 186 and 49,689. A core sample of 74 hospitals, which participated in all five surveys and included a mean of 23,871 patients per year, was analyzed separately.

Results: The overall prevalence rate of patients with nosocomial infections in the five studies was as follows: 1990, 8.5%; 1991, 7.8%; 1992, 7.3%; 1993, 7.1%; and 1994, 7.2%. The prevalence rate of patients with nosocomial infection in the core sample of 74 hospitals was 8.9%, 8.0%, 7.4%, 7.6%, and 7.6%, respectively (test for trend, P=.0001). Patients admitted to intensive care units had a 22.8% prevalence rate of nosocomial infection in 1994. The most common nosocomial infections by primary site were urinary tract infection and surgical site infections, followed by respiratory tract infections and bacteremia. More than 60% of all infections were supported by a microbiological diagnosis.

Conclusions: The EPINE project provides a uniform tool for performing limited surveillance of nosocomial infections in most Spanish acute-care hospitals. Its use helps to spread an accepted set of definitions and methods for nosocomial infection control in the Spanish healthcare system. The surveys indicate that the prevalence of nosocomial infections has been reduced over the last 5 years in a core sample of Spanish hospitals.

Comparing period prevalences with application to drug utilization

Period prevalence is frequently measured in studies based on administrative data such as that from health maintenance organizations. For example, treated prevalence and drug utilization prevalence are important measures that are typically defined in relationship to a specified time period. Often one wishes to compare administrative data with period prevalences based on national surveys. It may also be of interest to compare period prevalences from two (or more) different data sources. This comparison is not straightforward owing to the problem of "person-time at risk." This article reviews the values and drawbacks of period prevalence as compared with cumulative incidence. L ife table methodology is described for comparing period prevalence data from administrative databases with survey results. This technique can be extended to the comparison of period prevalence observations from two or more administrative data bases. Examples are given pertaining to hypnotic drug use and the treatment of schizophrenia.

Cardiovascular diseases in a Canadian Arctic population

OBJECTIVES

The purpose of this study was to review cardiovascular mortality, morbidity, and risk factors in the multiethnic population of the Northwest Territories, Canada.

METHODS

We analyzed death certificates and hospital records, and used a community health and examination survey.

RESULTS

The age-standardized mortality rate for ischemic heart disease (but not for other heart diseases or stroke) among the Northwest Territories population was lower than among the Canadian population. Among the indigenous Inuit/Eskimos and Indians, the age-standardized mortality rate for all circulatory diseases was lower than Canadians. Among Indian women, the rate approached the Canadian rate and exceeded that of Inuit and non-Natives. Compared with residents of Manitoba, Northwest Territories Inuit adults had a higher prevalence of smoking in all age-sex groups. Obesity was prevalent among older Inuit women and hypertension among young Inuit men. Except for women aged 25 to 44, the total cholesterol and triglyceride levels among Inuit were lower than or not different from Manitoba residents. Relatively high levels of high-density lipoprotein were found in older Inuits.

CONCLUSIONS

The epidemiologic pattern of cardiovascular diseases in Arctic Canada differs from that among non-Native, southern Canadians. Rapid sociocultural changes may alter the situation, and health agencies must anticipate such transitions and intensify culturally appropriate control programs.

Use of death certificates in epidemiological studies, including occupational hazards: discordance with clinical and autopsy findings

There has long been evidence of frequent inaccuracy of death certificates, with significant discordance between such designations and clinical and autopsy data. This exists for occupational diseases as well. The use of statistical rates based on death certificates has been seriously questioned despite their utility for total mortality. Programs to supplement death certificate data, particularly in occupational disease studies, may be helpful, and are reviewed.

A mathematic analysis of the "epidemiologic necropsy"

There has been much debate regarding the validity and implications of the "epidemiologic necropsy." Two opposing mathematic analyses have previously appeared--one by Flanders and O'Brien and one by Feinstein and colleagues. Because these analyses omitted discussion of certain key parameters and assumptions, I provide a more detailed analysis. I show that under the assumptions used by earlier authors, the observed ("registry") disease rates will equal the true disease rates, even if there is differential disease detection and large pool of undetected cases. Under realistic violations of assumptions, both the observed rates and the necropsy estimates will be biased. In any case, the data offered thus far are insufficient to accurately assess the impact of undetected disease on epidemiologic studies.