Person: Xu, Xin
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Publication Mammography Rates 3 Years After the 2009 US Preventive Services Task Force Guidelines Changes(American Society of Clinical Oncology (ASCO), 2015) Wharam, James; Landon, Bruce; Zhang, Fang; Xu, Xin; Soumerai, Stephen; Ross-Degnan, DennisPurpose In November 2009, the US Preventive Services Task Force (USPSTF) changed its mammography recommendations from every 1 to 2 years among women age ≥ 40 years to personalized screening decisions for women age 40 to 49 years and screening every 2 years for women age 50 to 74 years. Methods We studied mammography trends among 5.5 million women age 40 to 64 years enrolled in a large national health insurer. We used 2005 to 2009 mammography trends to predict 2012 rates. Our primary measure was the estimated difference between observed and predicted 2012 annual and biennial mammography rates. We stratified results by age group and race/ethnicity. Results Among women age 40 to 49 years, 2012 mammography rates declined by 9.9% (95% CI, −10.4% to −9.3%) relative to the predicted 2012 rate. Decreases were lowest among black women (−2.3%; 95% CI, −6.3% to 1.8%) and highest among Asian women (−17.4; 95% CI, −20.0 to −14.8). Annual mammography rates among women age 50 to 64 years declined by 6.1% (95% CI, −6.5% to −5.7%) by 2012. Regarding biennial mammography rates, women age 40 to 49 years experienced a 9.0% relative reduction (95% CI, −9.6% to −8.4%). White, Hispanic, and Asian women age 40 to 49 years demonstrated similar relative reductions of approximately 9% to 11%, whereas black women had no detectable changes (0.1%; 95% CI, −4.0% to 4.3%). Women age 50 to 64 years had a 6.2% relative reduction (95% CI, −6.6% to −5.7%) in biennial mammography that was similar among white, Hispanic, and Asian women. Black women age 50 to 64 years did not have changes in biennial mammography (0.4%; 95% CI, −2.6% to 3.5%). Conclusion Three years after publication of the 2009 USPSTF guidelines, mammography rates declined by 6% to 17% among white, Hispanic, and Asian women but not among black women. Small reductions in biennial mammography might be an unintended consequence of the updated guidelines.Publication Analyses of Associations Between Three Positionally Cloned Asthma Candidate Genes and Asthma or Asthma-related Phenotypes in a Chinese Population(BioMed Central, 2009) Zhou, Huanyu; Hong, Xiumei; Jiang, Shanqun; Dong, Hongxing; Xu, Xiping; Xu, XinBackground: Six asthma candidate genes, ADAM33, NPSR1, PHF11, DPP10, HLA-G, and CYFIP2, located at different chromosome regions have been positionally cloned following the reported linkage studies. For ADAM33, NPSR1, and CYFIP2, the associations with asthma or asthma-related phenotypes have been studied in East Asian populations such as Chinese and Japanese. However, for PHF11, DPP10, and HLA-G, none of the association studies have been conducted in Asian populations. Therefore, the aim of the present study is to test the associations between these three positionally cloned genes and asthma or asthma-related phenotypes in a Chinese population. Methods: Two, five, and two single nucleotide polymorphisms (SNPs) in the identified top regions of PHF11, DPP10, and HLA-G, respectively, were genotyped in 1183 independent samples. The study samples were selected based on asthma affectation status and extreme values in at least one of the following three asthma-related phenotypes: total serum immunoglobulin E levels, bronchial responsiveness test, and skin prick test. Both single SNP and haplotype analyses were performed. Results: We found that DPP10 was significantly associated with bronchial hyperresponsiveness (BHR) and BHR asthma after the adjustment for multiple testing; while the associations of PHF11 with positive skin reactions to antigens and the associations of HLA-G with BHR asthma were only nominally significant. Conclusion: Our study is the first one to provide additional evidence that supports the roles of DPP10 in influencing asthma or BHR in a Chinese population.Publication Heterozygosity Increases Microsatellite Mutation Rate, Linking it to Demographic History(BioMed Central, 2008) Amos, William; Flint, Jonathan; Xu, XinBackground: Biochemical experiments in yeast suggest a possible mechanism that would cause heterozygous sites to mutate faster than equivalent homozygous sites. If such a process operates, it could undermine a key assumption at the core of population genetic theory, namely that mutation rate and population size are indpendent, because population expansion would increase heterozygosity that in turn would increase mutation rate. Here we test this hypothesis using both direct counting of microsatellite mutations in human pedigrees and an analysis of the relationship between microsatellite length and patterns of demographically-induced variation in heterozygosity. Results: We find that microsatellite alleles of any given length are more likely to mutate when their homologue is unusually different in length. Furthermore, microsatellite lengths in human populations do not vary randomly, but instead exhibit highly predictable trends with both distance from Africa, a surrogate measure of genome-wide heterozygosity, and modern population size. This predictability remains even after statistically controlling for non-independence due to shared ancestry among populations. Conclusion: Our results reveal patterns that are unexpected under classical population genetic theory, where no mechanism exists capable of linking allele length to extrinsic variables such as geography or population size. However, the predictability of microsatellite length is consistent with heterozygote instability and suggest that this has an important impact on microsatellite evolution. Whether similar processes impact on single nucleotide polymorphisms remains unclear.Publication EFBAT: Exact Family-Based Association Tests(BioMed Central, 2007) Schneiter, Kady; Degnan, James H; Corcoran, Christopher; Xu, Xin; Laird, NanBackground: Family-based association tests are important tools for investigating genetic risk factors of complex diseases. These tests are especially valuable for being robust to population structure. We introduce a tool, EFBAT, which performs exact family-based tests of association for X-chromosome and autosomal biallelic markers. Results: The program EFBAT extends a network algorithm previously applied to autosomal markers to include the X-chromosome and to perform tests of association under the null hypotheses "no association, no linkage" and "no association in the presence of linkage" under additive, dominant and recessive genetic models. These tests are valid regardless of patterns of missing familial data. Conclusion: The general framework for performing exact family-based association tests has been usefully extended to the X-chromosome, particularly for the hypothesis of "no association in the presence of linkage" and for different genetic models.Publication High-Deductible Insurance and Delay in Care for the Macrovascular Complications of Diabetes(American College of Physicians, 2018-11-20) Wharam, J. Frank; Lu, Christine Y.; Zhang, Fang; Callahan, Matthew; Xu, Xin; Wallace, Jamie; Soumerai, Stephen; Ross-Degnan, Dennis; Newhouse, JosephBackground: Little is known about the long-term effects of high-deductible insurance on care for chronic medical conditions. Objective: To determine whether a transition from low-deductible to high-deductible insurance is associated with delays in the medical care for macrovascular complications of diabetes. Design: Observational comparison of matched groups. Setting: A large national health insurer during 2003-2012. Participants: The intervention group included 33,957 enrollees with diabetes who were continuously enrolled in low-deductible (