Purpose: Hispanic ethnicity is often used as a category for calculating population-based rates or assessing risk of epidemiologic studies. However, ethnic misclassification can lead to false conclusions unless the extent of misclassification and the characteristics of those misclassified are understood.
Methods: This study explored determinants of ethnic misclassification in a sample of 1154 cancer cases in the San Francisco-Oakland cancer registry, where ethnic classification is based on surname or medical record report. We compared the following: correctly classified Hispanics, persons classified as Hispanic who self-identified as non-Hispanic, and persons classified as non-Hispanic who self-identified as Hispanic.
Results: Among men classified as Hispanic, those most likely to self-identify as non-Hispanic did not speak Spanish, had non-Spanish surnames, and were recent immigrants. Women misclassified as Hispanic did not speak Spanish or have Spanish maiden names, nor did they have mothers with Spanish maiden names. Persons who called themselves Hispanic, but were misclassified by the registry, were likely to be non-Spanish speaking college-education males.
Conclusions: Researchers using ethnicity should be aware of how ethnicity was determined and how this classification may bias or confound their results.