Statistical Analyses
Statistical analyses were performed using SPSS 13.0 software (SPSS Inc.,
Chicago, Illinois, USA). The Kolmogorov-Smirnov test was used to analyze
the normality of the distribution of parameters. Continuous variables
are expressed mean±SD, while categorical variables are expressed as a
number (percentage). Comparison between 2 groups using the t test or
chi-squared test. Nonparametric variables are described as medians and
quartile ranges, and the comparisons between groups were made using
the Mann-Whitney test or the Kruskal-Wallis test. Patients were
classified into
C3low and
C3high groups by
grading the density of glomerular C3 deposition. The descriptive
analysis of the time reaching the primary and secondary endpoint was
performed by computing survival curves according to the Kaplan-Meier
method, and between-group survival was compared by the log-rank test.
Univariate and multivariate Cox proportional hazards models were used to
determine the factors associated with the risk of reaching the
creatinine doubling from baseline (multifailure model) or ESRD. Results
were expressed as hazard-rate (HRs) with CI. Univariate and multivariate
linear regression analyses were used to determine the associations
between the density of glomerular C3 deposition and other variables that
correlate with renal outcome. The multivariate models were built
considering that the main interest was the identification of prognostic
factors, present at the enrollment and statistically significant at
univariate analysis. Two-sided P values <0.05 were considered
statistically significant.