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Nicola Napoli, Steven Mumm, Reina Armamento‐Villareal, CYP1A1: Ethnic and Population Differences in Allelic Frequencies and Interpretation of Bone Biology Studies, Journal of Bone and Mineral Research, Volume 21, Issue 12, 1 December 2006, Pages 1960–1961, https://doi.org/10.1359/jbmr.060901
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We appreciate the comments of Giroux et al. on our manuscript “Effect of Polymorphisms of the CYP1A1 Gene on Estrogen Status and Bone Density,”(1 and we would like to address their concerns about our findings. First, they questioned that our allele frequency was higher than what had been reported and might be the result of erroneous genotype classification or bias in our population sample. We would like to remind their group that genotype/allele frequency varies according to ethnicity. From our review of the literature as shown in Table 1, it is evident that the frequency of the variant A allele is highly variable depending on the population under study; it is highest among Taiwanese women (19%)(2 and lowest among Spanish women (3.3%),(3 not to mention the 2.95% reported by Cascorbi et al.(4 among Germans as cited by Giroux et al. Accordingly, our allele frequency is within the range reported in the literature. Giroux et al. quoted the studies showing lower frequency but studies of higher A allele frequency had already been published, including one among French‐Canadians in 2001 by Krajinovic et al.,(5 with a population similar to that evaluated by Giroux et al. In that case‐control study on breast cancer, Krajinovic et al. reported the A allele frequency at 7.6% in healthy controls,(5 which is much higher than the 3.5% cited by Giroux et al., presumably in the same population. Similarly, our allele frequency was higher than what was reported in the study by Zhang et al.,(6 although both studies were done among postmenopausal white women living in the United States. We would like to point out, however, that it would be impossible for anyone to estimate the exact A allele frequency in the study of Zhang et al. considering that these investigators did not separate heterozygotes and homozygotes, and this was clearly stated in their report. The 4.5% frequency that Giroux et al. quoted was based on the assumption that all of the 37 patients carrying the variant A allele were heterozygotes and would underestimate the actual A allele frequency in the presence of homozygotes. In addition, our study was conducted among women living in the St Louis, MO, area compared with the study of Zhang et al., which was done in Connecticut. It is well recognized that the U.S. population is highly diverse in ancestry; in fact, the white women in our study are a composite of women of Anglo‐Saxon, Italian, Jewish, Irish, and German ancestry. Most likely, the women in the study of Zhang et al. came from diverse ancestry as well; however, the predominant ethnic group in their study population may be different than ours and may account for any difference in allele frequency.
