Elastase α-proteinase inhibitor and lactoferrin concentrations in endotracheal aspirates of ventilated newborns

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Abstract
Bacterial colonization of the tracheo‐bronchial tree is common and an established risk factor for infection in ventilated newborns. Elastase, a highly active proteinase, and lactoferrin, an iron‐binding protein and potential modulator of the inflammatory process, are both major constituents of either azurophilic or primary granules of neutrophilic granulocytes, released by activation of these cells during the inflammatory response. Since both elastase, complexed with its major inhibitor alpha1‐proteinase inhibitor (Eα1‐Pl), and lactoferrin (Lf) are indicators of granulocyte activation during bacterial infection, they may indicate infectious inflammation at the tracheobronchial site. To study whether these substances in a single suction probe may serve this purpose, we obtained 82 tracheo‐bronchial aspirates routinely from 16 ventilated newborns with a median gestational age of 31.5 (range, 25–39) weeks for laboratory analysis and bacterial cultures. Systemic inflammatory response by differential white blood cell count and C‐reactive protein (CRP) was monitored simultaneously. © 1992 Wiley‐Liss, Inc. The median Eα1‐PI level was significantly elevated in culture‐positive aspirates (1,005 μg/L: range, < 30–29,240 μg/L) in contrast to culture‐negative samples (158 (μg/L; range, < 30‐1,408 μg/L). In addition to a diagnostic sensitivity of 77%, Eα‐PI offered a high specifity of 88%, a positive predictive value of 97%, and a negative predictive value of 73%. In contrast, median Lf concentration (10.6; range, 0.3–58.3 mg/L vs. 11.7; range, 1.6–158 mg/L) showed no correlation with culture results. Of the culture‐positive aspirates 36% corresponded with systemic signs of an acute inflammatory response, such as elevated l/T‐ratio and CRP. As confirmed by serial measurements in a representative preterm neonate we suggest that an elevated Eα‐PI concentration in tracheo‐bronchial aspirates is a helpful additional indicator of local inflammation before it is detectable by a systemic inflammatory response.