Maureen Henderson

Validity of screening.

The technical aspects of evaluation of screening programs to detect early disease are discussed. Screening is differentiated from diagnosis. The practical importance of specificity and sensitivity of screening tests is illustrated. The concept of evaluation of the total program is introduced. The determinants of successful programs are discussed with illustrations.

A Population Survey of Symptoms Suggestive of Transient Ischemic Attacks

A sample of the Baltimore population was interviewed in order to determine the frequency of symptoms suggestive of transient cerebral ischemic attacks. Respondents were interviewed in their homes. A history of ten symptoms which may have occurred within the past two years was elicited. Of the 6,830 individuals that were interviewed, 52% had no symptoms and approximately 10% had three or more symptoms. The frequency of symptoms did not increase substantially with advancing age between ages 45 to 74 or very markedly by sex and race. Individuals reporting a history of cardiovascular disease, stroke or diabetes had a substantially higher frequency of symptoms. Also the frequency of symptoms appeared to be higher in the less-educated groups.

A study of hypertension in a black urban community: Preliminary epidemiologic findings

Abstract A prevalence survey of blood pressure levels among adult residents in a stratified random sample of central Baltimore City households showed geographical differences in prevalence rates. Variation in prevalence rates was associated with indices of socioeconomic status. High prevalence rates were associated with high rates of manifestation of severe disease. Measurements of end-organ damage and high blood pressure levels were used as manifestations of disease severity. The data describe the total prevalence of high blood pressure whether or not the elevation is under control. It, therefore, provides a complete estimate of the community hypertension burden. Indices of socioeconomic status can, incidentally, describe differential use of, or access to, sources of medical service. Interview data collected prior to initial blood pressure measurement were used to see how prevalence was related to individual perceptions of medical care availability and the use of different sources of medical service. The results of analysis showed an association between blood pressure control and availability of medical care. There was no association between availability of medical care and the proportion of free living hypertensive individuals known to the medical care system. The investigators believe that this preliminary analysis reflects the quality of personal care that goes with availability of medical services and the current mode of clinical practice which has virtually no impact on the identification of asymptomatic hypertensive individuals.

Screening—A privilege not a right

Screening is a mechanism to reduce the burden of disease in either the individual or the community or both. While the detection of most treatable disease usually promises elements of benefit to both the individual and the community, it does not necessarily follow that all disease detection has such dual benefit or indeed any benefit at all. The recognition and consequent removal from society of the leper in the absence of any effective treatment of leprosy was scarcely beneficial to the individual; at the other extreme, the detection and surgical treatment of a malignant tumor in an elderly retired man is an economic cost rather than a benefit to the community at large. Without available effective action against a disease, its early detection or prediction is of no benefit to anyone and may add substantial cost in terms of psychological distress to the cost of detection and palliative therapy. In an era of increasing public involvement in the general provision of medical care, it seems useful to divide screening procedures into those directed primarily toward reducing the impact of hazards which threaten the population as a whole, and those directed toward hazards which threaten individual members of the population. An approach to classification along these lines appears in Table I. Screening programs focused on control of infections, genetic disorders, and social hazards promise greater benefit to the community at large than to the individuals screened. Specific examples are chosen to illustrate horizontal transmission of disease, vertical transmission of disease, and threats to groups of the population who find themselves within the sphere of influence of a limited number of diseased or subversive individuals. The screened individuals benefit more than their community when screening programs are directed to the control of conditions which cause disability, distress, or death with minimal embarrassment of community resources. The extent to which a community or nation derives economic benefit from the application of effective screening procedures depends upon the extent to which society bears the cost of medical and health care and the living expenses of the disabled. The cost to a comprehensively planned system can be reduced by measures which limit skilled manpower demands, maximize technical assistance, and reduce the incidence, duration, and severity of disease. Table II classifies screening procedures into types on the basis of four characteristics and provides one or more examples of each. The procedures are first divided into those designed to detect actual disease and those designed

The impact of legal abortion: redefining the maternal mortality rate.

INDUCED ABORTION is associated with several clinical and demographic measures. Recent reports have demonstrated the relative safety of early surgical termination of -pregnancy (1-3) as well as the relationship between legal abortion and a decline in birth rates and fertility indices (4,5). New York City data suggest that out-of-wedlock births may also be decreased, and Evrard (6) has further suggested that widespread use of abortion may affect the maternal and perinatal mortality rates. In this paper we will examine the effect of varying utilization of induced abortion on the maternal mortality rate and the relationship between nonviable conceptions and the measurement of maternal risk. We will attempt to show the limitations of the traditional maternal mortality rate as a measure for describing or comparing maternal risks for different cohorts. Alternative methods of measurement will be discussed. The traditional maternal mortality rate is expressed as the ratio of the number of maternal deaths (numerator) to the live births (denominator) in a defined population per unit of time. It seems likely that the rationale for the traditional measure stems from the fact that live births were the most readily obtainable quantity useful for measuring maternal risk. In addition, we might speculate that it is derived from a notion of a cost to benefit ratio-the cost in maternal deaths for the benefit of a given number of live births, that is, the cost of successful reproduction. When the large majority of known pregnancies ended in live births, the traditional maternal mortality rate (TMMR) represented an adequate measure of pregnancy risk which was useful for both descriptive and comparative purposes. Because conceptions ending in spontaneous or induced abortion were difficult to ascertain, their relationship to the maternal mortality rate could not be fully appreciated. The legalization of induced abortion has resulted in a substantial increase in knowledge concerning the incidence of

Evaluation of cancer screening programs. Parallels with clinical trials

The methodologic limitations of available observational evidence for the evaluation of ongoing cancer control programs is reviewed. The specific example of Control Programs for Cervical Cancer is chosen to illustrate these limitations. These limitations pertain to the special features of the natural history of this disease, to the types of data available as well as to problems in the interpretation of these data. Given the unacceptability of conducting a rigorous randomized clinical trial of an ongoing and accepted cancer control procedure, an alternative experimental approach is proposed. This approach consists in the random allocation of census tracts with a high risk population to either of two groups: 1) an experimental group in which active and repeated screening activities will attempt to reach virtually all susceptible women, 2) a comparable control group which will only benefit from regularly available services.

Analytical bias in studies of pregnancy outcome

Abstract This report has described three types of bias introduced into analyses of studies of pregnancy. In each case the bias came from selection of patients for final analysis. The application of the examples of bias described is not restricted to studies of pregnancy outcome. Any comparative study continued over an interval of time is open to similar opportunities for selection leading to similar problems of bias. It is hoped that this report will emphasize the need to control selection during the study or to use adjusted rates during analysis.