Long-term outcome and IL-6 levels in critically ill septic patients: results from the sepsis longitudinal epidemiological outcomes tracking study (SELECT I)

Methods

The SELECT I study is a prospective, multi-center, observational study to assess the long-term clinical and economic outcomes in patients with sepsis from presumed infectious etiology during and beyond their acute care hospitalization, along with the clinical, economic, and prognostic relevance of baseline IL-6 levels, as measured by a dichotomous rapid test (SEPTEST™: ST-positive and ST-negative readings with a cut-off at about 1000 pg/ml [1]). All eligible patients with standard clinical criteria for severe sepsis were enrolled from ICUs in 52 centres in six European countries during the study period (May 1998–October 2000). The SEPTEST™ was administered within 24 hours after inclusion in the study. Patients received usual care and were observed in the ICUs until death or discharge. After discharge the vital status and the functional and general health status (EuroQol 5D) were collected at days 30, 60, 90 and 180 following study entry. The main focus of the analysis reported here is the comparison of the survival rates in the ST-positive and ST-negative groups (Kaplan–Maier curves).

Results

Data was derived from the initial 350 patients of a total of 433 enrolled patients. Of these, 113 (32.3%) were ST-positive, 237 (67.7%) were ST-negative. There was no evidence of an association between IL-6 status and either gender, age, co-morbid condition upon admission, major interventions during hospitalization, or participation in a clinical trial. Table 1 shows the survival by group (ST-negative, overall, ST-positive). The survival difference between ST-positive and ST-negative is highly significant (P < 0.0001, log rank test). The difference on day 30 was 17.3% (95% CI: 6.5%, 28.2%) and remains nearly stable during follow-up (day 60: 23.9%, day 90: 1.9%, day 180: 19.8%).

Table 1 Survival rates

Conclusions

Overall mortality observed in this study is in the range expected in critically ill patients with severe sepsis/septic shock. However, a remarkable statistically significant difference between patients with high (ST-positive) and low (ST-negative) baseline IL-6 titers are observed. The excess mortality in the ST-positive patients occurs mostly before day 30 (i.e. in the acute phase of the condition). After this time the hazard of death seems to remain similar in the two groups over the observation time of 180 days after study entry. The study confirms the high prognostic value of IL-6 for mortality in severe sepsis as reported by others [1].

Acknowledgement

Funded by a grant from Abbott Laboratories, Chicago, IL, USA.