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November 19, 2003

Factors in Studying Patient-Physician Communication—Reply

Author Affiliations

Letters Section Editor: Stephen J. Lurie, MD, PhD, Senior Editor.

JAMA. 2003;290(19):2544. doi:10.1001/jama.290.19.2544-a

In Reply: We agree with Dr Mealiffe that a sex-ratio ascertainment bias does exists in our cohort of families. As he points out, by selecting families with at least 3 cases of breast and/or ovarian cancer, we also selected families with at least 3 females. Less obvious sources of bias may also have been present, as Mealiffe suggests. Indeed, we have some evidence of a modest sex-ratio ascertainment bias present in our cohort of families with breast and/or ovarian cancer. A slight excess of male births is well documented in the general population. For example, according to the Spanish National Statistics Institute,1 48.6% of all Spanish newborns were female in the year 2001. In contrast with the cohort we described in our article, we observed a similar sex ratio (47.1% female births; 328 females vs 368 males) when considering as a whole 45 HNPCC pedigrees ascertained according to Amsterdam criteria in our cancer clinic.2 However, in our study we reported a slight excess of female births in 50 pedigrees with breast and/or ovarian cancer with no detectable BRCA1 mutation (53% female births; 519 females vs 465 males). We think that the observed increase in female births from approximately 49% in the general population to 53% in families with breast and/or ovarian, but no BRCA1 mutations, is most likely due to the ascertainment bias indicated by Mealiffe. Nevertheless, as all families in our study were similarly ascertained for genetic testing, our data show that the ascertainment bias (which does exist) cannot by itself explain the sex ratio observed in pedigrees with BRCA1, either as a whole or in the offspring of BRCA1 carriers.

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