Practice nurses should routinely collect data on ethnicity from all patients, recommend researchers from the University of Warwick.
They warn that if this does not become standard, patterns of disease in different ethnic groups will continue to be missed, as ethnicity data collection is currently so poor.
Small studies by the charity Cancer Research UK have previously suggested trends such as a low incidence of breast cancer among South Asian women and that black women tend to develop the disease earlier than those from other ethnic groups.
But such findings cannot be confirmed on a wider scale because the data is not collected, said Janet Dunn, chief investigator of the Warwick Medical School team.
The researchers examined information from a GP practice in Nuneaton, questioned health professionals and patients, and conducted a literature review. Of 15,058 patients enrolled at the practice, 91% had no ethnicity stated on their records.
A third of the nurses and GPs questioned said they did not routinely collect ethnicity data, citing such reasons as lack of understanding, resources or training. Focus groups of 36 patients showed people did not object to declaring their ethnic background, but there was a feeling that categories were outdated and limited.
The authors recommended increasing awareness and training for health professionals, so they could ask patients about ethnicity with confidence.
At first enrolment into primary care or first hospital visit was the ideal time to collect this information through patient self-reporting, they said.
This should be double checked during their consultation, with an opt-out option for those patients who do not want to say. This should be linked to hospital databases so the information only has to be given once.
Language, religion and country of birth should also be included as old categories based on census data do not account for cultural differences, they told a South Asia Group meeting last month at Warwick University.