address = administration of drotrecogin alfa ( activated ) in early stage severe sepsis ; apache = acute physiology and chronic health evaluation ; drotaa = drotrecogin alfa ( activated ) ; prowess = recombinant human activated protein c worldwide evaluation of severe sepsis . jf was involved with the conception and design of the study , acquisition , analysis and interpretation of data , and wrote the first draft of the manuscript . na was involved with the conception and design of the study , analysis and interpretation of data , and critical revision of the manuscript for important intellectual content . mm was involved with the interpretation of data and critical revision of the manuscript for important intellectual content . relative risk ( rr ) and 95% confidence intervals ( 95% ci ) for 28-day mortality in each study . n / n = number of deaths at 28 days divided by the total number of patients randomly assigned to drotrecogin alfa ( activated ) or placebo . for the phase ii trial , only patients who were randomized to the same dose and duration of drotrecogin alfa ( activated ) used in the recombinant human activated protein c worldwide evaluation of severe sepsis ( prowess ) and administration of drotrecogin alfa ( activated ) in early stage severe sepsis ( address ) trials are included . results are classified by low - risk and high - risk subgroups from the recombinant human activated protein c worldwide evaluation of severe sepsis ( prowess ) and administration of drotrecogin alfa ( activated ) in early stage severe sepsis ( address ) trials , defined by either acute physiology and chronic health evaluation ( apache ii ) score ( less than 25 , and 25 or more ) or organ failure ( single and multiple ) . weight refers to the contribution of each study to the overall pooled estimate of treatment effect for each low - risk and high - risk subgroup . the weight of each study is calculated as the inverse of the variance of the natural logarithm of its relative risk . the size of the symbol denoting each point estimate approximates the weighting of each study to each pooled effect measure . each pooled effect measure is calculated with the use of a random - effects model . n / n = number of deaths at 28 days divided by the total number of patients in each particular subgroup randomly assigned to drotrecogin alfa ( activated ) or placebo . the numbers of patients and deaths at 28 days in each subgroup were estimated from data provided in references ,   and   for the prowess trial , and in references   and   for the address trial .