Ethnicity: A missing variable when defining normative values for reporting echocardiographic studies

Abstract

The effectiveness of any diagnostic test is dependent upon the ability of the test to accurately detect abnormal-ities. An assumption of reliability and validity underlies all medical tests and echocardiography is no exception. The identification of ‘abnormal’ relies on the definition of ‘normal’ and needs to acknowledge normal physi-ological variation that may arise from factors such as age, body size, gender, and ethnicity (1). So far, the studies that have been designed to obtain the normative values for echocardiographic measurements have related the mea-sured parameters to subjects’ age, height, weight, body surface area and gender. Only a few have taken into ac-count the role of ethnicity. As a result current guidelines for chamber quantification by echocardiography (2) con-tains reference values that have been obtained from Eu-ropean (Western Europe) and American (United States) Caucasian subjects. However, ethnicity is an important factor and studies which have compared measurements performed in Caucasians, Indians, Malaysian and Chi-nese (3, 4), Japanese (5, 6) or African American (7) subjects have shown significant differences in measurements be-tween the different ethnical groups. Therefore, the use of the reference values reported in current guidelines to define normality or abnormality of cardiac chamber size and function in population others than European and White Americans may be misleading and bring to errone-ous conclusions.This is not only a medical problem of the areas of the world non-represented in current guidelines like Middle-East, Asia, Africa or South America but, since more and more people move from their area of origin to different areas of the world for working, tourism or to escape from war or persecution this lack of proper reference values is becoming a worldwide medical problem. Accordingly, several initiatives have been undertaken to collect nor-mative data from larger cohorts of normal subjects who may include different ethnicities (8, 9). The EchoNoRMAL study is an individual person data meta-analysis of echo-cardiographic measurements obtained from healthy subjects aimed to re-define normal echocardiographic reference ranges (for the left heart including dimensions, areas, volumes, and associated calculated variables) for populations across the world, and to do that, the organiz-ing Institution (the University of Auckland, New Zealand) asked data from those populations to the different rease-archers around the world (9). However, when they looked at the data of almost 70,000 healthy subjects collected from several institutions around the world they discov-ered that there were no data about people from South America, Africa and Middle-East (Poppe KK and Whalley G, personal communication).With this background in mind, the study by Sadegh-pour et al. (10) published in the Archives of Cardiovascu-lar Imaging assumes particular scientific relevance. To the best of my knowledge, this is the first report about echocardiographic reference values for cardiac chambers obtained from normal Iranian subjects. Since the data where obtained in a large cohort of carefully screened healthy subjects they will definitely fill an existing gap in our knowledge. The study by Sadeghpour et al. (10) is also valuable because they used state of the art echocardio-graphic systems with second harmonic imaging, made a comprehensive echo study which included Doppler flow and tissue Doppler analysis and were able to pro-vide the results stratified by gender and age decades. In summary they provided a comprehensive framework to be used to discriminate between normal and abnormal echocardiographic measurements in that population. Not surprisingly they found that cardiac chambers of Iranian subjects are smaller and limits of normality are lower than those reported in current guidelines (2). From the clinical point of view it means that if reference values