Classification of sepsis, severe sepsis and septic shock: the impact of minor variations in data capture and definition of SIRS criteria

To quantify the effects of minor variations in the definition and measurement of systemic inflammatory response syndrome (SIRS) criteria and organ failure on the observed incidences of sepsis, severe sepsis and septic shock. We conducted a prospective, observational study in a tertiary intensive care unit in The Netherlands between January 2009 and October 2010. A total of 1,072 consecutive adults were included. We determined the upper and lower limits of the measured incidence of sepsis by evaluating the influence of the use of an automated versus a manual method of data collection, and variations in the number of SIRS criteria, concurrency of SIRS criteria, and duration of abnormal values required to make a particular diagnosis. The measured incidence of SIRS varied from 49 % (most restrictive setting) to 99 % (most liberal setting). Subsequently, the incidences of sepsis, severe sepsis and septic shock ranged from 22 to 31 %, from 6 to 27 % and from 4 to 9 % for the most restrictive versus the most liberal measurement settings, respectively. In non-infected patients, 39-98 % of patients had SIRS, whereas still 17-6 % of patients without SIRS had an infection. The apparent incidence of sepsis heavily depends on minor variations in the definition of SIRS and mode of data recording. As a consequence, the current consensus criteria do not ensure uniform recruitment of patients into sepsis trials.