Gallstone Size and the Risk of Gallbladder Cancer

To the Editor.— The article by Diehl 1 that investigated gallstone size and the risk of gallbladder cancer presented some valuable cross-cultural data. Unfortunately, the article did not specify the method used to determine ethnicity. It is imperative to know whether Mexican origin was self-reported, determined on the basis of language spoken, interviewer observed, or determined on the basis of the person's surname, as each method yields varying results. 2 More importantly, if self-reporting was not used, it is entirely possible (even though there is a large Mexican-American population residing in San Antonio, Tex) that Hispanics other than those of Mexican origin were included in the Mexican-American sample. Furthermore, Diehl differentiated cancer cases on the basis of whether patients were born in a Latin American country. It seems to us that, if the Mexican-American sample excluded non-Mexican-origin Hispanics, birth in Mexico would have been the preferred basis for comparison, especially