Socioeconomic and racial/ethnic differences in the discussion of cancer screening: "between-" versus "within-"...

To determine the extent to which socioeconomic and racial/ethnic differences in cancer screening discussion between a patient and his/her primary care physician are due to "within-physician" differences (the fact that patients were treated differently by the same physicians) versus "between-physician" differences (that they were treated by a different group of physicians).

We use data from the baseline patient and physician surveys of two community trials from the Communication in Medical Care (CMC) research series. The two studies combined provide an analysis sample of 5,978 patients ages 50-80 nested within 191 primary care physicians who practiced throughout Southern California.

Our main outcomes of interest are whether the physician has ever talked to the patient about fecal occult blood test (FOBT; for colorectal cancer screening), mammogram (for breast cancer screening, female patients only) and the prostate-specific antigen test (PSA, male patients only). We consider five racial/ethnic groups: non-Hispanic white, non-Hispanic black, Hispanic, Asian, and other race/ethnicity. We measure socioeconomic status by both income and education. For each type of cancer screening discussion, we first estimate a probit model that includes patient characteristics as the only covariates to assess the overall differences. We then add physician fixed effects to derive estimates of "within-" versus "between-" physician differences.

There was a strong education gradient in the discussion of all three types of cancer screening and most of the education differences arose within physicians. Disparities by income were less consistent across different screening methods, but seemed to have arisen mainly because of "between-physician" differences. Asians were much less likely, compared with whites, to have received discussion about FOBT and PSA and these differences were mainly "within-physician" differences. Black female patients, however, were much more likely, compared with whites treated by the same physicians, to have discussed mammogram with their physicians.

Differences in cancer screening discussion along the different dimensions of patient SES may have arisen because of very different mechanisms and therefore call for a combination of interventions. Physicians need to be aware of the persistent disparities by patient education in clinical communication regarding cancer screening and tailor their efforts to the needs of low-education patients. Quality-improvement efforts targeted at physicians practicing in low-income communities may also be effective in addressing disparities in cancer screening communication by patient income.