Alveolar neopterin, procalcitonin, and IL-6 in relation to serum levels and severity of lung injury in ARDS

Abstract

To the Editor,Tsantes et al. evaluated plasma and bronchoalveolar lavage fluid (BALF) procalcitonin (PCT) and interleukin-6 (IL-6) in discriminating septic from non-septic causes of acute respiratory distress syndrome (ARDS) [1]. They concluded that early plasma, but not BALF-PCT concen-trations, can help distinguish between septic and non-septic ARDS causes and are associated with the severity of multiple organ dysfunction syndrome in septic ARDS patients. In addition to PCT and IL-6 we want to point out the role of alveolar and serum neopterin and PCT in the early phase of ARDS and acute lung injury (ALI) as a valu -able marker of increased activity of the cellular immune system [2]. Elevated levels of neopterin in serum and BALF in various lung diseases, e.g., sarcoidosis and interstitial lung disease, have been reported [3]. Pneumonia was associated with significantly elevated neopterin levels in BALF compared to controls [4]. Serum PCT determination in early ARDS was used to discriminate between septic and non-septic underlying disease [5]. PCT was detectable in BALF of patients with severe lung contusion, however, it failed to be a reliable parameter in the assessment of lung contusion severity [6]. IL-6 concentrations are high in the BALF of patients at risk for ARDS and remain elevated throughout the course of ARDS [7].We would like to contribute the so far unpublished results of a previous study concerning alveolar and serum neopterin, PCT and IL-6 in the early phase of ARDS and ALI. In our study, we measured neopterin, PCT, granulo-cyte colony-stimulating factor (G-CSF), TNF-α, IL-6, IL-8, epithelial neutrophil-activating peptide (ENA)-78, soluble TNF-α receptor type I (sTNF-RI), soluble TNF-α receptor type II (sTNF-RII), IL-1 receptor antagonist (IL-1RA), and IL-10 in BALF and serum within 12 and 24 h after onset of ARDS/ALI. Alveolar G-CSF, IL-8, and ENA-78 in relation to serum levels, pulmonary neutrophilia, and severity of lung injury in ARDS, and the association of endogenous G-CSF with anti-inflammatory mediators in patients with ARDS have been published previously [8, 9]. Addition-ally, we determined the concentration of neopterin, PCT, IL-6 in lung epithelial lining fluid (ELF) by using the urea dilution method for estimating the volume of ELF in the lavaged lung segment [10].We evaluated levels of neopterin, PCT, and IL-6 in BALF, ELF and serum for comparison of the concentra-tions of these compounds between the blood circulating compartment and the alveolar space. Furthermore, we evaluated whether there is a difference between ARDS and ALI, septic and non-septic ARDS/ALI, survivors and non-survivors or a correlation to lung injury expressed as PaO