Soluble triggering receptor correlated with severity of lung contusion after trauma. Soluble triggering receptor on myeloid cells-1 (sTREM-1) levels in bronchoalveolar lavage (BAL) 16 hours after trauma (solid symbols) and 40 hours after trauma (white symbols) after lung contusion, grouped by severity of lung contusion (based on initial CT scan) in a semi-logarithmic scale. sTREM-1 levels correlated at both time points with increasing severity of contusion (16 hours: P < 0.01, correlation coefficient = 0.461 (Spearman rank order correlation); and 40 hours: P < 0.001, correlation coefficient = 0.582). The differences in sTREM-1 levels in BAL 16 hours and 40 hours after trauma were significant between the groups with no contusion (only 40 hours after trauma) and with mild versus severe lung contusion (Dunn's method). Differences in sTREM-1 levels additionally reached significance between day 1 and day 2 for the group with severe contusion (P < 0.05, Wilcoxon signed rank test).