Ethnic misclassifications hamper progress in research

Editor—McDowell et al review the evidence for ethnic differences in susceptibility to adverse drug reactions to cardiovascular drugs.¹ They concluded that patients from different ethnic groups have different risks for adverse reactions to cardiovascular drugs and that ethnic group may be one determinant of harms of a given treatment, either because it acts as a surrogate measure of genetic make up or because cultural factors alter the risk.

Clearly, there are important issues that are worth discussing with regard to this study's approach of ethnic classifications and its conclusions. The ethnic differences in health are not easily explained, and better definitions and terminology, and greater attention to population heterogeneity are a prerequisite for scientific progress.² The heterogeneity of African descent populations,² Asian,³ and white⁴ populations has long been pointed out. Some journals, including the BMJ, have also set standards by publishing explicit guidelines for the use of race and ethnicity. Despite this, broad terms such as black, Asian, or non-black are still entrenched in scientific writing.

The continuing use of broad terms in epidemiology and public health may reflect pragmatic reasons such as small study numbers; but the need for simplicity should be weighed against the dangers of stereotyping and incorrectness. The authors' conclusion that ethnic group may be one determinant of harms of a given treatment in the individual patient because it acts as a surrogate measure of genetic make up is worrying given the nature of ethnic classifications in their study.

Ethnicity and health researchers should move beyond the straightforward black-white category that was the dominant and limiting approach for most of the 20th century and access the substantial ethnic diversity that typifies the population under study.