Investigation of the freely available easy-to-use software 'EZR' for medical statistics

Abstract

Although there are many commercially available statistical software packages, only a few implement a competing risk analysis or a proportional hazards regression model with time-dependent covariates, which are necessary in studies on hematopoietic SCT. In addition, most packages are not clinician friendly, as they require that commands be written based on statistical languages. This report describes the statistical software 'EZR' (Easy R), which is based on R and R commander. EZR enables the application of statistical functions that are frequently used in clinical studies, such as survival analyses, including competing risk analyses and the use of time-dependent covariates, receiver operating characteristics analyses, meta-analyses, sample size calculation and so on, by point-and-click access. EZR is freely available on our website (http://www.jichi.ac.jp/saitama-sct/SaitamaHP.files/statmed.html) and runs on both Windows (Microsoft Corporation, USA) and Mac OS X (Apple, USA). This report provides instructions for the installation and operation of EZR.

Figure 1

Main window of EZR.

Figure 2

(a) Dialog for plotting KM curves and performing a log-rank test. (b) KM curves of overall survival grouped according to the stem cell source.

Figure 3

(a) Point estimations, s.e. and 95% confidence intervals of survival rate at each time point. (b) The results of log-rank test. (c) Summary of the survival analyses copied to the clipboard and then pasted into a spreadsheet.

Figure 4

(a) Dialog for performing a Cox proportional hazards regression. (b) Dialog for plotting cumulative incidence curves and performing Gray's test.

Figure 5

(a) Main result of Cox proportional hazard regression that includes the hazard ratios, their 95% confidence intervals and P-values for each explanatory variable, followed by the results of three tests for the global null hypothesis. (b) Summary of proportional hazards regression analysis, the results of Wald test and the results of testing the proportional hazards assumption. (c) Results of stepwise selection of explanatory variables.

Figure 6

(a) Cumulative incidence curves of relapse (event=1) and non-relapse mortality (event=2) grouped according to the stem cell source. (b) Summary of the cumulative incidence analyses copied to the clipboard and then pasted into a spreadsheet. (c) Stacked cumulative incidence graph. The light gray area indicates the incidence of relapse (event=1) and the dark gray area indicates the incidence of non-relapse mortality (event=2).