The cases were paired with 87 unrelated controls randomly and progressively selected from visitors to the same hospital center. Controls and cancer patients were the same gender and age, from the same community and from the same ethnic group. Controls had no family medical history of cancer, systemic diseases or chronic inflammations.
Los casos fueron apareados con 87 controles no relacionados, seleccionados aleatoria y progresivamente de los visitantes al mismo centro hospitalario, del mismo género y edad, pertenecientes a la misma comunidad y grupo étnico, sin historia personal ni familiar de cáncer, ni de enfermedades sistémicas o inflamatorias crónicas.