RESUMO
Objective: To systematically introduce the design of case-cohort study and the statistical methods of relative risk estimation and their application in the design. Methods: First, we introduced the basic principles of case-cohort study design. Secondly, Prentice's method, Self-Prentice method and Barlow method were described in the weighted Cox proportional hazard regression models in detail, finally, the data from the Shanghai Women's Health Study were used as an example to analyze the association between obesity and liver cancer incidence in the full cohort and case-cohort sample, and the results of parameters from each method were compared. Results: Significant association was observed between obesity and risk for liver cancer incidence in women in both the full cohort and the case-cohort sample. In the Cox proportional hazard regression model, the partial regression coefficients of the full cohort and the case-cohort sample fluctuated with the adjustment of confounding factors, but the hazard ratio estimates of them were close. There was a difference in the standard error of the partial regression coefficient between the full cohort and the case-cohort sample. The standard error of the partial regression coefficient of the case-cohort sample was larger than that of the full cohort, resulting in a wider 95% confidence interval of the relative risk. In the weighted Cox proportional hazard regression model, the standard error of the partial regression coefficient of Prentice's method was closer to the parameter estimates from full cohort than Self-Prentice method and Barlow method, and the 95% confidence interval of hazard ratio was closer to that of the full cohort. Conclusions: Case-cohort design could yield parameter results closer to the full cohort by collecting and analyzing data from sub-cohort members and patients with the disease, and reduce sample size and improve research efficiency. The results suggested that Prentice's method would be preferred in case-cohort design.
Assuntos
Feminino , Humanos , China/epidemiologia , Estudos de Coortes , Modelos de Riscos Proporcionais , Risco , Tamanho da AmostraRESUMO
<p><b>OBJECTIVE</b>To investigate the association between the polymorphism of HLA-DRB1 alleles and type 2 diabetes mellitus in Yi nationality of Yunnan.</p><p><b>METHODS</b>Polymerase chain reaction-sequence specific primers (PCR-SSP) genotyping method was conducted in 79 patients with type 2 diabetes mellitus and 47 ethnically matched controls in Yi Nationality Autonomous Prefecture, Chuxiong.</p><p><b>RESULTS</b>HLA-DR7 and DR11 allele frequencies in type 2 diabetic mellitus patients were significantly higher than those in non-diabetic control subjects respectively(P is 0.009, RR is 8.329;P is 0.029, RR is 7.734).</p><p><b>CONCLUSION</b>DR7 and DR11 alleles are probably susceptible genes of type 2 diabetes mellitus in Yunnan Yi nationality.</p>
Assuntos
Adulto , Idoso , Idoso de 80 Anos ou mais , Humanos , Masculino , Pessoa de Meia-Idade , Alelos , Sequência de Bases , China , Diabetes Mellitus Tipo 2 , Genética , Frequência do Gene , Predisposição Genética para Doença , Genética , Antígenos HLA-DR , Genética , Cadeias HLA-DRB1 , Dados de Sequência Molecular , Análise de Sequência de DNARESUMO
<p><b>OBJECTIVE</b>To investigate the association between the polymorphism of HLA-DQA1 alleles and type 2 diabetes in Yi nationality of Yunnan.</p><p><b>METHODS</b>Polymerase chain reaction with sequence-specific primers (PCR-SSP) genotyping method was conducted in 58 ethnic Yi patients with type 2 diabetes mellitus and 82 ethnically matched controls from Chuxiong of Yunnan. Then a study was made on the association between the polymorphism of HLA-DQA1 alleles and type 2 diabetes mellitus.</p><p><b>RESULTS</b>The frequency of HLA-DQA1*0301 allele in the patients with type 2 diabetes mellitus was significantly higher than that in the healthy controls (P=0.002, RR=3.097), and the frequency of HLA-DQA1*0601 in the patients was significantly lower (P=0.025, RR=0.429).</p><p><b>CONCLUSION</b>In Yi nationality of Yunnan, HLA-DQA1*0301 allele may be a susceptible gene and the HLA-DQA1*0601 allele may protect individuals from the risk of diabetes mellitus.</p>
Assuntos
Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , China , Diabetes Mellitus Tipo 2 , Genética , Predisposição Genética para Doença , Genética , Antígenos HLA-DQ , Genética , Cadeias alfa de HLA-DQ , Reação em Cadeia da Polimerase , Polimorfismo GenéticoRESUMO
<p><b>OBJECTIVE</b>To investigate the association between the polymorphism of HLA-DQA1 alleles and type 2 diabetes mellitus in Yunnan Hans.</p><p><b>METHODS</b>Polymerase chain reaction-sequence specific primers(PCR-SSP) genotyping method was conducted in 108 Han patients with type 2 diabetes and 56 ethnically matched controls from the same area of Yunnan Province.</p><p><b>RESULTS</b>HLA-DQA1*0301(RR=3.092, P<0.01) and DQA1*0501 (RR=3.257, P<0.05) allelic frequencies in type 2 diabetic patients were significantly higher than those in non-diabetic control subjects respectively. HLA-DQA1*0401 (RR=0.371, P<0.01) allelic frequencies in patients were significantly decreased, compared with controls; HLA-DQA1*0302 (RR=3.356, P<0.01) allelic frequencies in patients with type 2 diabetic nephropathy were significantly increased.</p><p><b>CONCLUSION</b>HLA-DQA1*0301 and DQA1*0501 are susceptible genes of type 2 diabetes in Yunnan Han nationality; in reverse, HLA-DQA1*0401 is a resistant gene. HLA-DQA1*0302 is a susceptible gene of type 2 diabetic nephropathy.</p>