Epi Info™ User Guide

Analysis Commands: KMSURVIVAL

Description
This command performs the Kaplan-Meier Survival Analysis and produces graphs and statistics for one or several groups of subjects being followed in a clinical study. At any given time, some of the subjects may be “censored,” not having information available on their status. KMSurvival is especially constructed to deal with this situation. Statistics showing the risk set by group and time can be written to an OUTTABLE for later formatting.

Syntax
KMSURVIVAL <time variable>=<group variable> * <censor variable> (<value>) [TIMEUNIT=”<time unit>”] [OUTTABLE=<tablename>] [GRAPHTYPE=”<graph type>”] [WEIGHTVAR=<weight variable>]

• The <time variable> represents the variable specifying the time of the event.
• The <group variable> represents the variable that indicates to which treatment or control group the subject belongs.
• The <censor variable> represents the variable to describe an event as failure or censored.
• The <value> represents the value of the censor variable indicating uncensored (failure).
• The <time unit> represents a value for labeling the time axis.
• The <graph type> represents the following:
  • Survival Probability is the observed survival over the different groups.
  • Log-Log Survival is the log of the negative log of the survival probability.
  • None does not produce a graph. If no graph type is specified, the default Survival Probability curve is plotted.
• The <weight variable> represents a variable in the database that specifies the contribution or each data row to the output.

Example
The commands below show a comparison between two groups.

READ {.\Projects\Sample\Sample.prj}:Addicts
KMSURVIVAL Survival_Time_Days = Clinic * Status ( 1 ) TIMEUNIT="Days"