ARDS of early or late onset: does it make a difference?

BACKGROUND: Differences in outcomes have been demonstrated for critically ill patients with late-onset compared with early-onset renal failure and late-onset compared with early-onset shock, which could cause a lead-time bias in clinical trials assessing potential therapies for these conditions. We used data from a large, multicenter observational study to assess whether late-onset ARDS was similarly associated with worse outcomes compared with early-onset ARDS.
METHODS: Data were extracted from the Sepsis Occurrence in Acutely Ill Patients (SOAP) study, which involved 198 ICUs from 24 European countries. All adult patients admitted to a participating ICU between May 1, 2002 and May 15, 2002, were eligible, except those admitted for uncomplicated postoperative surveillance. Early/late onset acute lung injury (ALI)/ARDS was defined as ALI/ARDS occurring within/after 48 h of ICU admission.
RESULTS: Of the 3,147 patients included in the SOAP study, 393 (12.5%) had a diagnosis of ALI/ARDS; 254 had early-onset ALI/ARDS (64.6%), and 139 (35.5%) late-onset. Patients with early-onset ALI/ARDS had higher Simplified Acute Physiology II scores on admission and higher initial Sequential Organ Failure Assessment scores. Patients with late-onset ALI/ARDS had longer ICU and hospital lengths of stay than patients with early-onset ALI/ARDS. ICU and hospital mortality rates were, if anything, lower in late-onset ALI/ARDS than in early-onset ALI/ARDS, but these differences were not statistically significant.
CONCLUSIONS: There were no significant differences in mortality rates between early- and late-onset ARDS, but patients with late-onset ALI/ARDS had longer ICU and hospital lengths of stay.