Differences In Prevalence Of Disease Research Articles

A Cross-Cultural Comparison of Critical Care Delivery: Japan and the United States

To compare the utilization and outcomes of critical care services in a cohort of hospitals in the United States and Japan. Prospective data collection on 5,107 patients and detailed organizational characteristics from each of the participating Japanese study hospitals between 1993 and 1995, with comparisons made to prospectively collected data on the 17,440 patients included in the US APACHE (acute physiology and chronic health evaluation) III database. Twenty-two Japanese and 40 US hospitals. Consecutive, unselected patients from medical, surgical, and mixed medical/surgical ICUs. Severity of illness, predicted risk of in-hospital death, and ICU and hospital length of stay (LOS) were assessed using APACHE III. Japanese ICU directors completed a detailed survey describing their units. US and Japanese ICUs have a similar array of modalities available for care. Only 1.0% (range, 0.56 to 2.7%) of beds in Japanese hospitals were designated as ICUs. The organization of the Japanese and US ICUs varied by hospital, but Japanese ICUs were more likely to be organized to care for heterogeneous diagnostic populations. Sample case-mix differences reflect different disease prevalence. ICU utilization for women is significantly lower (35.5% vs 44.8% of patients) and there were relatively fewer patients > or = 85 years old in the Japanese ICU cohort (1.2% vs 4.6%), despite a higher per capita rate of individuals > or = 85 years old in Japan. The utilization of ICUs for patients at low risk of death significantly less in Japan (10.2%) than in the United States (12.9%). The APACHE III score stratified patient risk. Overall mortality was similar in both national samples after accounting for differences in hospital LOS, utilizing a model that was highly discriminating (receiver operating characteristic, 0.87) when applied to the Japanese sample. The application of a US-based mortality model to a Japanese sample overestimated mortality across all but the highest (> 90%) deciles of risk. Significant variation in expected performance was noted between hospitals. Risk-adjusted ICU LOS was not significantly longer in Japan; however, total hospital stay was nearly twice that found in the US hospitals, reflecting differences in hospital utilization philosophies. Similar high-technology critical care is available in both countries. Variations in ICU utilization reflect differences in case-mix and bed availability. Japanese ICU utilization by gender reflects differences in disease prevalence, whereas differences in utilization by age may reflect differences in cultural norms regarding the limits of care. Such differences provide context from which to assess the delivery of care across international borders. Miscalibration of predictive models applied to international data samples highlight the impact that differences in resource use and local practice cultures have on outcomes. Models may require modification in order to account for these differences. Nevertheless, with large databases, it is possible to assess critical care delivery systems between countries accounting for differences in case-mix, severity of illness, and cultural normative standards facilitating the design and management such systems.

Guidelines for interpretation of electron beam computed tomography calcium scores from the Dallas Heart Disease Prevention Project

I the past decade, treatment of patients with coronary artery disease has increasingly focused on altering the properties of the atherosclerotic plaque. Until recently, there has been no noninvasive method to detect the presence of coronary artery plaque in the absence of flow-limiting stenoses. The development of a new generation of computed tomography (CT) scanners capable of detecting small amounts of coronary calcium represents an important advance in the noninvasive identification of higher risk patients with nonobstructive atherosclerosis. Patients with excessive coronary calcium based on ageand genderspecific reference values are at higher risk for obstructive and nonobstructive coronary disease, and probably for coronary events as well.1–6 Although most experts agree that asymptomatic patients with excessive coronary calcium should receive intensified preventative care, there are few data upon which to make treatment recommendations. Although there is controversy as to which patients should undergo this screening test, the emergence of for-profit imaging centers and direct-to-consumer advertising has led to significant numbers of self-referred patients with abnormal test results seeking treatment advice. Unfortunately, many existing treatment algorithms based on calcium score include recommendations for unproven therapies such as antioxidant vitamins and recommendations for expensive testing including stress testing, angiography, and coronary revascularization. The Dallas Heart Disease Prevention Project is a large cross-sectional epidemiologic study designed to study the gene-environment interactions causing cardiovascular disease in the ethnic populations of Dallas County. As part of this study, approximately 3,000 randomly selected Dallas County residents aged 30 to 60 years will undergo electron beam CT (EBCT). Although 1 goal of this study is to better understand how to interpret EBCT results, the study ethics committee mandated that participants be informed of test results and their physicians be provided guidelines for interpretation. Until clinical trial data become available, there are no “evidence-based” guidelines for the prevention of cardiovascular events based on EBCT results, particularly in the case of asymptomatic patients. Thus, as part of this project, we have developed guidelines that incorporate the calcium score with current National Cholesterol Education Panel (NCEP) guidelines. There are 2 accepted modalities for detection of coronary calcium, EBCT and helical CT. EBCT has slightly shorter image acquisition time, but there have been no definitive studies comparing the 2 modalities to determine which is superior for the detection of coronary calcium. With use of EBCT during a single breath-hold, the patient’s heart is imaged in 3-mm cross-sectional slices. The resolution of the scan allows identification of coronary arteries, and the coronary calcium is readily visible in contrast to the soft tissues of the heart. Several commercially available software analysis packages allow easy identification of calcium deposits and calculation of calcium deposit area. The area of the calcified plaque is then multiplied by a coefficient based on peak x-ray density yielding a plaque-specific calcium score. The total calcium score is the sum of the scores for each individual plaque. The degree of calcium of the coronary arteries correlates directly with the degree of coronary athersclerosis when the total calcium score is related to the total amount of plaque in the coronary tree.1,4,7–9 However, areas of calcium on EBCT do not necessarily represent significant coronary stenoses. Most of the data relating calcium scores with presence and degree of atherosclerosis come from studies of symptomatic populations. Generalizing these results to an asymptomatic population may not be appropriate because of differences in disease prevalence. However, in asymptomatic subjects the reported sensitivity of EBCT in detecting obstructive coronary approaches 90%, and the average reported specificity is 55%.1 Particularly in younger adults (,40 years), significant atherosclerosis can be present without any detectable calcium by EBCT.1,10 Although the sensitivity of the test increases with age, the specificity of the test decreases with age because calcification occurs gradually in an age-independent process. Women develop calcium on average at later ages than men, and median calcium scores for women are similar to median scores of men aged #10 years.10 Because coronary calcium increases with age and From the Department of Internal Medicine, Division of Cardiology, The University of Texas Southwestern Medical School, Dallas, Texas. The report was supported by grants from the Donald W. Reynolds Foundation, Las Vegas, Nevada; and the American Heart Association Texas Affiliate, Austin, Texas. Manuscript received October 30, 2000; revised manuscript received and accepted January 22, 2001. Address for reprints: Thomas C. Andrews, MD, Consultants in Cardiology, 1300 West Terrell Avenue, Suite 500, Fort Worth, Texas 76104. E-mail: tandrews@hcin.net.

Association of specific allergen sensitization with socioeconomic factors and allergic disease in a population of Boston women

Background: Socioeconomic differences in allergic disease prevalence have been reported; asthma has been associated with poverty in the United States and hay fever and eczema with relative affluence elsewhere. It is not yet established to what degree such differences in disease prevalence reflect patterns of sensitization and specific allergen sensitivities. Objective: We analyzed specific and total IgE measurements in a sample of 458 women, enriched for allergic disease, from the metropolitan Boston area to establish the relation of allergen sensitization to markers of socioeconomic status (SES) and to the prevalence and socioeconomic pattern of allergic disease in this community. Methods: Total and specific IgE antibodies were measured with the UNICAP System; self-reported allergic disease, household income, education, and race-ethnicity were ascertained with a questionnaire; and a further marker of poverty (percentage living below the poverty level) in the women’s area of residence was established on the basis of zip codes. Analysis was performed with SAS statistical software. Results: Markers of low SES were univariately associated with increases in total IgE, number of allergen sensitizations, and levels of specific IgE. Socioeconomic differences in sensitization to cockroach (35% vs 6% in the highest and lowest poverty areas), animal (44% vs 26%), and ragweed (49% vs 23%) allergens were most marked. Sensitization primarily to indoor inhalant allergens (not ragweed or ryegrass) were associated with an increased risk of asthma, even after adjustment for SES. Conclusion: We have demonstrated a socioeconomic gradient in sensitization that concords with increased rates of asthma in less affluent communities in this population. (J Allergy Clin Immunol 2001;107:615-22.)

The Editors’ Choice

The Editors’ Choice

An approach to demonstrating cost-effectiveness of diagnostic imaging modalities in Australia illustrated by positron emission tomography.

The aim of this study was to develop a framework in which the cost-effectiveness of new imaging technologies could be evaluated using data from other countries, while assessing the impact that any differences between the study populations and Australia may have upon the results. Publications reporting the cost-effectiveness or therapeutic impact of positron emission tomography (PET) were re-worked using Australian cost structures. PET was assigned a cost of $950. The effects of potential differences between the populations studied and the Australian population were evaluated by applying sensitivity analysis to those publications that describe decision tree methodology. The parameters included in the sensitivity analysis were disease prevalence and specificity of PET. The Australian cost savings per patient examined by PET were $505.50-$912.41 for investigation of solitary pulmonary nodules, $34.65-$360.03 for lung cancer staging, $550.08 for axillary staging of breast cancer, $230.75-$2301.27 for assessment of recurrent colorectal cancer and $300.24-$2069.65 for assessment of myocardial viability. Significant differences in disease prevalence and PET specificity could occur while the cost-effectiveness of PET was preserved. Decision tree sensitivity analysis can demonstrate the cost-effectiveness of diagnostic imaging modalities in Australia and provides indications that PET is cost-effective for a range of clinical indications.

NIMH genetics initiative millennium schizophrenia consortium: Linkage analysis of African-American pedigrees

The NIMH Genetics Initiative is a multi-site collaborative study designed to create a national resource for genetic studies of complex neuropsychiatric disorders. Schizophrenia pedigrees have been collected at three sites: Washington University, Columbia University, and Harvard University. This article-one in a series that describes the results of a genome-wide scan with 459 short-tandem repeat (STR) markers for susceptibility loci in the NIMH Genetics Initiative schizophrenia sample-presents results for African-American pedigrees. The African-American sample comprises 30 nuclear families and 98 subjects. Seventy-nine of the family members were considered affected by virtue of having received a DSMIII-R diagnosis of schizophrenia (n = 71) or schizoaffective disorder, depressed (n = 8). The families contained a total of 42 independent sib pairs. While no region demonstrated evidence of significant linkage using the criteria suggested by Lander and Kruglyak, several regions, including chromosomes 6q16-6q24, 8pter-8q12, 9q32-9q34, and 15p13-15q12, showed evidence consistent with linkage (P = 0.01-0.05), providing independent support of findings reported in other studies. Moreover, the fact that different genetic loci were identified in this and in the European-American samples, lends credence to the notion that these genetic differences together with differences in environmental exposures may contribute to the reported differences in disease prevalence, severity, comorbidity, and course that has been observed in different racial groups in the United States and elsewhere.

Health-related quality of life associated with lower urinary tract symptoms in four countries

Objectives. To describe health-related quality of life (HRQL) associated with lower urinary tract symptoms (LUTS) assessed by validated questionnaires in four countries. Methods. More than 6000 men, recruited by using community- or population-based sampling in four countries, completed questionnaires soliciting information about urinary symptom frequency, bother, degree of interference with daily activities, and other measures of HRQL. Results. In all countries, disease-specific HRQL worsened with increasing age. Adjusting for age, most disease-specific HRQL measures were significantly worse with increasing symptom severity. The correlation between symptoms and HRQL was strongest in countries with higher prevalence of symptoms, such as Japan or the United States, and less pronounced in countries with lower prevalence (France, Scotland), possibly reflecting the lower variability in scores. Conclusions. HRQL measures are worse in older men, and increased urinary symptom severity is associated with worse disease-specific HRQL in all countries, despite potential cross-cultural differences in disease prevalence, medication use, perceptions, or willingness to report symptoms or worse HRQL. This cross-cultural consistency suggests that an assessment of symptom bother or interference with daily activities may be useful in patient evaluation.

Clinical decision making, risk and occupational therapy.

Little is known about the processes involved in risk taking, and complex decision making of the type encountered on acute medical wards in general hospitals. The purpose of the present study was to examine certain of these processes in the context of decisions to discharge elderly inpatients from hospital. Vignettes of hypothetical frail and disabled elderly in-patients were presented to student and qualified occupational therapists (OTs). All the vignettes represented high risk discharges and each of the patients expressed the desire to return to their own home. The additional diagnosis of early dementia was manipulated within and between vignettes. Subjects were asked to decide on the appropriateness of discharging each patient to (a) home and (b) a residential or nursing home. In addition, subjects completed a short demographic questionnaire which also probed aspects of their knowledge about elderly people. Results indicated that qualified OTs were less likely to overrule patients' wishes by favouring discharge of patients to residential or nursing home, and more likely to favour discharge to patients' own homes than student OTs. There was no overall main effect of dementia on subjects' decisions. In addition to clinical experience, certain areas of knowledge about elderly people were significantly associated with different approaches to risk taking in response to the vignettes. Undergraduate syllabi may need to be modified to incorporate more information about elderly people, the prevalence of different diseases, and direct experience of clinical decision making in the context of uncertain and risky situations.

Sensitization to inhaled allergens as a risk factor for asthma and allergic diseases in Chinese population

Background: Allergen sensitization is associated with asthma and allergic disease in children, but such a relationship has not been confirmed in Chinese populations. Objective: The objective of this study was to evaluate the effects of allergen sensitization and family history of atopy on asthma and allergic disease in Chinese schoolchildren from three southeast Asian populations. Methods: Written questionnaires on respiratory and allergic symptoms were completed by parents of children of secondary-school age (age range 12 to 18 years) in Hong Kong ( n = 1062), Kota Kinabalu in eastern Malaysia ( n = 409), and San Bu in southern China ( n = 737). A subsample of schoolchildren underwent skin prick testing to common inhalant allergens (Hong Kong 471 children, Kota Kinabalu 321, San Bu 647). Results: The prevalence of asthma and allergic disease in schoolchildren was highest in Hong Kong, intermediate in Kota Kinabalu, and lowest in San Bu. However, the overall rate of atopic sensitization was similar in the three populations (49% to 63%). House dust mite and cockroach were the two most common allergens causing sensitization and these gave rise to more than 95% of the positive skin test results in all three populations. By regression analysis, mite allergy was associated with rhinitis and asthma in all three populations, and a family history of asthma, rhinitis, or eczema was strongly associated with respective symptoms in the subjects. After adjusting for age, sex, atopic status, and family history of allergic disease, the place of residence remained a significant independent factor for asthma (odds ratio [OR] = 1.0 for Hong Kong, 0.57 for Kota Kinabalu, 0.15 for San Bu, p < 0.001), rhinitis (OR = 1.0 for Hong Kong, 0.59 for Kota Kinabalu, 0.15 for San Bu, p < 0.001), or eczema (OR = 1.0 for Hong Kong, 0.35 for Kota Kinabalu, 1.01 for San Bu, p < 0.001). Conclusion: Sensitization to indoor allergens was a significant risk factor for asthma and allergic disease, and familial clustering of disease was common in the region. However, the marked difference in disease prevalence in the three southeast Asian populations of Chinese schoolchildren cannot be explained by atopic sensitization and family history alone, and the place of residence was an independent risk factor for asthma and allergies, which suggests an important environmental role in disease pathogenesis. (J Allergy Clin Immunol 1997;99:594-8.)

Pathoses associated with mandibular third molars subjected to removal

Objective To measure the prevalence of disease of mandibular third molars referred for removal and to estimate the risk for development of pathoses for two cues. Study design A prospective cohort study on molars subjected to removal was performed. The prevalence of different diseases and the patient's age, angular position, and degree of impaction of the molars were registered. Odds ratio for molars with different positions and impaction states were estimated. Results Pericoronitis was found in 64% of cases, caries in the third molar in 31%, periodontitis in association with 8%, caries in the second molar in 5%, and root resorption of the second molar with 1% of the molars with pathoses. Odds ratio was highest for distoangular molars (5.8) and for molars partially covered by soft tissue (6.7). Conclusions The odds ratio is about 22 and 34 times higher for molars partially covered by soft tissue than for molars completely covered by soft or bone tissue. For distoangular molars the odds ratio is 5 to 12 times higher than for molars in other positions.

Sex-specific differences in coronary artery disease risk factors, evaluation, and treatment: Have they been adequately evaluated?

Women constitute a significant, growing proportion of patients at risk for acute coronary events. Analyses of the pathophysiology, prevention, diagnosis, and management of coronary disease in women have been hampered in that most clinical trials have studied predominantly male populations. For example, most diagnostic studies have not accounted for sex-specific differences in prevalence of disease or for confounding factors. Disease management in women has also been guided by outcomes data from mostly male populations. Although a review shows no sex-specific differences in relative risk reduction from treatment, it remains possible that differences exist, given the under-representation of women in trials. Including adequate numbers of women in future trials is important yet costly, because of the larger total sample size required. Nevertheless, continued inquiry is required to answer the questions raised by current investigations.

Heterogeneity of familial risk in sarcoidosis

Familial clustering of sarcoidosis and the higher prevalence and clinical severity of sarcoidosis in African Americans suggests etiologic heterogeneity. To test for heterogeneity in familial risk of sarcoidosis, we studied 3,395 siblings and parents of 558 index cases (361 African American, 197 Caucasian) diagnosed at Henry Ford Hospital between 1951 and 1994. Using the age- and sex-specific cumulative incidence of sarcoidosis in our sample, we found a statistically significant heterogeneity in familial risk of disease (P < .001). To determine if this was due to a greater risk of sarcoidosis in African Americans, we recalculated disease probabilities using age-, sex-, and race-specific disease cumulative incidence and found the same amount of heterogeneity in familial risk (P < .001). Index cases (n = 69) from high-risk families were more likely to be African American (odds ratio [OR] = 3.24; 95% confidence interval (CI) = 1.71−6.14) and to have an offspring or second-degree relative affected (OR = 6.21; 95% CI = 2.86−13.45). We conclude that the heterogeneity of familial sarcoidosis risk found in this study is supportive of multiple etiologies. Our results also show that a quantitative assessment of familial risk based on siblings and parents may be a useful screening tool for identifying families with additional affected members. Of the high-risk families, African Americans made up a greater-than-expected percentage even after accounting for differences in disease prevalence. We suggest targeting African Americans for studies of sarcoidosis that focus on Mendelian hypotheses and genetic linkage. © 1996 Wiley-Liss, Inc.

Heterogeneity of familial risk in sarcoidosis.

Familial clustering of sarcoidosis and the higher prevalence and clinical severity of sarcoidosis in African Americans suggests etiologic heterogeneity. To test for heterogeneity in familial risk of sarcoidosis, we studied 3,395 siblings and parents of 558 index cases (361 African American, 197 Caucasian) diagnosed at Henry Ford Hospital between 1951 and 1994. Using the age- and sex-specific cumulative incidence of sarcoidosis in our sample, we found a statistically significant heterogeneity in familial risk of disease (P < .001). To determine if this was due to a greater risk of sarcoidosis in African Americans, we recalculated disease probabilities using age-, sex-, and race-specific disease cumulative incidence and found the same amount of heterogeneity in familial risk (P < .001). Index cases (n = 69) from high-risk families were more likely to be African American (odds ratio [OR] = 3.24; 95% confidence interval (CI) = 1.71-6.14) and to have an offspring or second- degree relative affected (OR = 6.21; 95% CI = 2.86-13.45). We conclude that the heterogeneity of familial sarcoidosis risk found in this study is supportive of multiple etiologies. Our results also show that a quantitative assessment of familial risk based on siblings and parents may be a useful screening tool for identifying families with additional affected members. Of the high-risk families, African Americans made up a greater-than-expected percentage even after accounting for differences in disease prevalence. We suggest targeting African Americans for studies of sarcoidosis that focus on Mendelian hypotheses and genetic linkage.

Epizootiology of morbillivirus infection in North American harbor seals (Phoca vitulina) and gray seals (Halichoerus grypus).

A longitudinal study of morbillivirus infection among harbor (Phoca vitulina) and gray (Halichoerus grypus) seals on the Atlantic coast of North America was carried out between 1980 and 1994. Serology also was carried out on harbor seals from the Pacific northwest coast collected in 1992 and 1993. The prevalence of morbillivirus neutralizing antibodies was significantly (P < 0.0001) higher in gray (73%, n = 296) than in harbor seals (37%, n = 387) from the Atlantic. Titers were significantly (P < 0.0001) higher against phocine distemper (PDV) compared to any other morbillivirus. Antibodies were not detected in serum from Pacific harbor seals. During the winter of 1991 to 1992 an epizootic occurred among harbor seals on the northeast coast of the United States. The event was characterized by an increase in strandings and by a significant (P = 0.001) increase in PDV antibody prevalence to 83% (n = 36) in seals stranded that winter. Morbillivirus lesions and antigen were observed in six animals found stranded from southern Maine to Long Island, New York (USA), between November 1991 and April 1992. In addition, morbillivirus encephalitis was detected in tissues from a harbor seal that stranded in 1988. Enzootic infection appeared to be present in both seal species, although with a different prevalence of disease. We propose that enzootic infection among gray seals is facilitated by population size, high annual recruitment and innate resistance to clinical disease. Infection may be maintained in the smaller harbor seal population through casual contact with gray seals.

Grommets, tonsillectomies, and deprivation in Scotland

To see whether there is a relation between grommet insertion operation and tonsillectomy rates, otolaryngology services, and deprivation scores in Scotland. Analysis of routine 1990 NHS data on grommet insertions and tonsillectomies in Scottish children aged 0-15 years compared with data on general practitioner and otolaryngology services and Carstairs deprivation scores. All 15 Scottish health boards. All children aged 0-15 (1,021,933). Tonsillectomy was more common than grommet insertion operations in Scotland (6182:4850). Health boards with high grommet insertion rates were more likely to have low tonsillectomy rates (Spearman's rank correlation -0.59; 95% confidence interval -0.87 to -0.03). Grommet insertion rates varied fourfold (from 2.4/1000 to 9.2/1000) and tonsillectomy rates twofold (from 3.6/1000 to 8.0/1000) across Scottish health boards. Variation between health boards had changed over the 15 years 1975-90. Variation in grommet insertion rates did not reflect variation in the supply of otolaryngology consultants (Spearman's rank correlation -0.25). There was a non-significant tendency for high general practitioner referral rates to be associated with high grommet insertion rates, low tonsillectomy rates, and less deprived areas (Spearman's rank correlation coefficients 0.50, -0.53, and -0.43). Deprivation (measured by Carstairs scoring for each health board) was associated with higher tonsillectomy rates (Spearman's rank correlation 0.41; 95% confidence interval -0.22 to 0.80) and significantly lower grommet insertion rates (-0.73; -0.92 to -0.28). Social factors as well as differences in disease prevalence and medical practice need to be considered when studying variation in childhood grommet insertion and tonsillectomy rates.

The effect of smoking on health service utilization.

This study involved direct observation of the differences in prevalence of disease and utilization of medical care by smokers, non-smokers, and ex-smokers. The data was collected from the 1989 Korean National Health Survey (1989 KNHS). A total of 5,201 individuals ages 20 to 59 were randomly selected from the whole Korean population using the three-stage stratified random sampling. Based on the logistic regression, the following results were obtained. Compared with the non-smokers, the relative risks for an acute disease were 1.9 and 1.7 for male ex-smokers and female current smokers, respectively. Smoking behavior significantly increased utilization of health services such as admissions (RR = 2.5 for current smokers) among females, outpatient visits (RR = 2.1 for ex-smokers, RR = 2.3 for age began to smoke was less than 18 years) among males and (RR = 1.5 for current smokers) among females. Furthermore, the utilization of outpatient services for ex-smokers who were self-concerned about their health was 3.4 times higher than the non-smokers. Based on the weighted least square regression model the days of medication for male current smokers and ex-smokers were significantly longer than non-smokers. These effects persisted after controlling for major identified confounding factors. Thus, the results of this study confirmed that smoking is an important cause of diseases and a major contributing factor to the use of health services.

Blood Pressure and Skin Color

<h3>Tb the Editor.—</h3> The study by Klag et al¹typifies a common fallacy in epidemiologic studies: the assumption of concordanceof genetically variable traits in human populations.²In fact, the distributions of different traits are typically discordant. A common misconception is that if a trait or disease is more or less prevalent in blacks, it must be related to skin color, since this is how we classify individuals into races. It is not widely appreciated that race is a social construct, not a biologically meaningful one; therefore, one should study sociocultural variables to help explain observed racial differences in disease prevalence.2 Klag et al demonstrate this very convincingly. Unfortunately, the casual reader may be left with the impression that a link has been found between skin color and disease. In our own work,^3,4we have sought to refute the equally illogical claim that osteoporosis is associated with decreased skin pigmentation because it is more prevalent in whites. In this case, there is some logical biochemical con

Clinical Prediction Rule for Pulmonary Infiltrates

To derive and validate a clinical rule for predicting pneumonic infiltrates in adult patients with acute respiratory illness. Prevalence studies in three settings. Emergency departments of the University of Illinois Hospital at Chicago, the University of Nebraska Medical Center at Omaha, and the Medical College of Virginia at Richmond. Symptoms, signs, comorbidity data, and chest roentgenogram results were recorded for 1134 patients from Illinois (the derivation set), 150 patients from Nebraska, and 152 patients from Virginia (the validation sets). All patients presented to the emergency department and had a chest roentgenogram to evaluate fever or respiratory complaints. Within the training set, temperature greater than 37.8 degrees C, pulse greater than 100 beats/min, rales, decreased breath sounds, and the absence of asthma were identified as significant predictors of radiographically proved pneumonia in a stepwise logistic regression model (P = 0.001). The logistic rule discriminated patients with and without pneumonia in the training set with a receiver operating characteristic (ROC) area of 0.82. In the validation sets, the rule discriminated pneumonia and nonpneumonia with ROC areas of 0.82 and 0.76 after adjusting for differences in disease prevalence (P greater than 0.2 compared with the training set). The predicted probability of having pneumonia for patients with different clinical findings corresponded closely with the incidence of pneumonia among patients with such findings in the three settings. Among adults presenting with acute respiratory illness, a prediction rule based on clinical findings accurately discriminated patients with and without radiographic pneumonia, and was used in two other samples of patients without significant decrement in discriminatory ability. This rule can be used by physicians to develop more effective strategies for detecting pneumonia and for helping to determine the need for radiologic study among patients with acute respiratory disease.

Hematopoietic neoplasia inMya arenaria: Prevalence and indices of physiological condition

A field survey of hematopoietic neoplasia (Hn) in the soft shell clamMya arenaria (L.) was undertaken using an immunoperoxidase diagnostic technique. Monthly collections ofM. arenaria were made at two sites: Little Buttermilk Bay and New Bedford Harbor, both in Buzzards Bay, Massachusetts, USA, from May 1986 to October 1987. Clams were diagnosed for leukemia and analyzed for soft-tissue dry weight, condition index, and carbon and nitrogen content of the soft tissue. Prevalence of leukemia inM. arenaria exhibited a seasonal fluctuation with a maximum prevalence in fall (September to October) and a minimum prevalence in early summer (March to July). A second maximum peak in late winter (January to March) was observed at one site. Leukemia primarily affected clams that were 3 to 4 yr post-settlement. Lower prevalence levels were observed in both younger and older clams. LeukemicM. arenaria with advanced stages of the disease, were in poorer physiological condition based on dry weight of the soft tissue, condition index, and carbon content of the tissue. Nitrogen metabolism appeared to be unimpaired. Significant differences were observed between the two sites with respect to prevalence of Hn and the physiological condition of clams. Differences in disease prevalence between the two sites may be the result of unknown environmental factors that facilitate initiation of the disease or, that compromise the defense mechanisms of the clams.

The Importance of Disease Prevalence in Transporting Clinical Prediction Rules

Because clinical prediction rules often are applied in new settings to calculate the probability of a disease, we evaluated the accuracy of three rules for predicting streptococcal pharyngitis in 310 patients. Use of the rules led to overestimations of disease probability in 47%, 82%, and 93% of the patients. When we used receiver-operating characteristic curve analysis, no rule lost power to discriminate streptococcal from nonstreptococcal causes of pharyngitis. The overestimations in disease probability likely were caused by differences in disease prevalence between our setting (5%) and the settings in which they were developed (15% to 17%). All rules led to accurate predictions when they were adjusted for the disease prevalence found in our setting using a likelihood ratio formulation of Bayes' theorem. The value of prediction rules, like that of other diagnostic tests, is affected by differences in disease prevalence in different settings. Failure to recognize and adjust for these differences may cause poor decision making or the premature dismissal of valid rules.