Computational protocol: IL-6 rs1800795 polymorphism is associated with septic shock-related death in patients who underwent major surgery: a preliminary retrospective study

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Protocol publication

[…] For the description of the study population, p values were estimated with nonparametric tests: Mann–Whitney U test was used for continuous variable and Chi-squared/Fisher’s exact test for categorical variables. For the genetic association study, the survival analysis (Kaplan–Meier and Cox regression analyses) was used to compare the outcome variables according to the presence of IL-6 rs1800795 CC genotype. Data were analyzed using dominant, recessive and additive models, which were tested according to the goodness of fit evaluated by Akaike’s information criterion (AIC) value and Bayesian information criterion (BIC).Follow-up was censored at 90 days. Survival probabilities were estimated using the Kaplan–Meier product-limit method at 7, 28, and 90 days and compared using the log-rank test. Cox regression analyses were used to investigate the relationship of IL-6 rs1800795 polymorphism with the outcome variable during the first 7, 28, and 90 days. Each Cox regression test was adjusted by the most significant covariables for each outcome variable, avoiding the overfitting of the regression. The covariables were selected by stepwise algorithm in a multivariate model. We included the SNP [enter algorithm (forced entry for the SNP)] and the most relevant characteristics by stepwise algorithm (at each step, factors are considered for removal or entry: a p value for entry and exit of 0.15 and 0.20, respectively). The covariables used were APACHE-II score, gender, age, antibiotic treatment, type of surgery (cardiac or abdominal), elective surgery (emergency or scheduled), peritonitis, comorbidities [obesity, diabetes heart disease, chronic obstructive pulmonary disease (COPD)], hypertension, neoplasia, liver disease, smoker, and high alcohol intake. All statistical analyses were performed by using the IBM SPSS Statistics for Windows, version 21.0 (IBM Corp, Chicago, Armonk, NY, USA).In addition, Hardy–Weinberg equilibrium (HWE) analyses were computed by Haploview 4.2 software, considering equilibrium when p > 0.05. […]

Pipeline specifications

Software tools SPSS, Haploview
Applications Miscellaneous, GWAS
Organisms Homo sapiens
Diseases Heart Diseases, Hypertension, Infection