BMC Cancer 2007, 7:201 http://www.biomedcentral.com/1471-2407/7/201 Discussion Despite overall improvements in mammography screen- ing nationwide, there remain disparities in screening among certain population subgroups, including Asians. This study, an analysis of data from a large, population- based sample of Asian women in California, takes advan- tage of a novel statistical method with the ability to iden- tify discrete subgroups of women who do not appear to be following screening guidelines. This method identified two important characteristics defining Asian women in this category: 1) those who have never had a pap exam to screen for cervical cancer, and 2) those who do not use hormone therapy, have osteoporosis, or have not had a hysterectomy. Previous studies have not reported any of these characteristics as predictors of mammography use. We also found that among women meeting either 1) or 2) above, those with no usual source of health care, were also likely to not follow mammography screening guidelines. Having no usual source of health care has been reported previously as a determinant of mammography use [12,14,24]. Our findings suggest that Asian women who do not follow mammography screening recommenda- tions also do not follow guidelines for other cancer screening tests and may not have good access to health care, so effective programs to improve screening in these groups should focus not just on mammography but on all cancer screening tests. Women's health issues may be a key discriminator of regular recipients of mammograms, as this finding suggests that women may be referred or reminded more often by their physician to obtain mam- mograms and/or are more diligent about their health in general. In addition, providers treating these conditions may be more likely to be specialists in women's health, and thus more diligent in referring patients to mammog- raphy screening. Furthermore, the relationship between using hormone replacement therapy, and possibly treat- ment for osteoporosis, and breast cancer etiology may result in increased vigilance and surveillance for cancer [42,46-49] thereby prompting providers to recommend routine mammograms for these women. However, it does not appear that routine use of the health care system for other health issues is related to mammography use, as having arthritis, asthma, diabetes, or high blood pressure was not associated with having a mammogram in the past two years in our analysis. Additional focus should be placed on primary care physicians to promote age-appro- priate cancer screening. Health plans should also have sys- tems enabling health personnel to issue reminders or even schedule screening appointments for patients who are being seen for other health issues. The heterogeneity of Asians as a single group [50] is sup- ported by our subgroup-specific findings, and should be emphasized when developing programs targeting specific Asian ethnic communities. Specifically, Chinese non-citi- zens were at highest risk for not having a mammogram within the past two years. Citizenship status has not pre- viously been shown to be a determinant of mammogra- phy use; it may be related to predictors of mammography use found in other studies such as poorer language profi- ciency, decreased acculturation, and foreign birth [17- 19,22,24-27,29-31], although language, education, and birthplace did not emerge as being particularly salient pre- dictors in our study. Being a U.S. citizen may also be asso- ciated with having health insurance benefits, familiarity with and trust in Western biomedicine and facility in nav- igating the American health care system. Among Filipinas who have had pap or colorectal cancer screening, having health insurance was the next strongest delineator of adherence to screening guidelines among Filipinas; this characteristic has been noted elsewhere [27]. Other than pap screening, Korean women without women's health issues and either public or no health insurance had the lowest mammography use, and this finding is supported by previous studies showing lack of insurance as a barrier to mammography screening [51]. In South Asians, we found that despite having health insurance and being employed, non-citizens under age 50 were at high risk of not having a mammogram. Among Vietnamese women, pap screening was an important predictor, as was single marital status, a finding reported previously [17,18,24,26]. Future studies should focus on elucidating explanations of these predictors, and outreach efforts to target these subgroups, particularly among South Asian and Vietnamese women, for whom considerably less research has been conducted. This study has a number of strengths. We used RP, an emerging but currently under-used, powerful statistical technique to identify meaningful subgroups of Asian women at high-risk for not following mammogram screening recommendations. RP is suitable for identifying high-risk subgroups as it creates combinations of variables that best describe mammography use. Because of the exploratory nature of this technique, we found several fac- tors associated with mammography use that have not pre- viously been shown in the literature. However, RP also confirmed other factors, such as health insurance and marital status, which have previously been shown to be associated with mammography screening among Asians, suggesting that RP can be reliably applied to this research question. This technique was applied recently to a pro- spective study of 1229 African-American and White women in Connecticut to similarly identify subgroups of women who did not adhere to mammogram screening guidelines [33]. Our study, however, is the first, to our knowledge to apply RP to a large population-based behav- ioral risk factor survey to address this issue among Asian American women. The large sample size in this study allowed for analysis of most of the Asian ethnic subgroups Page 9 of 12 (page number not for citation purposes)