Stability of interleukin 8 and neutrophil elastase in bronchoalveolar lavage fluid following long-term storage

Abstract

Background Interleukin-8 (IL-8) and neutrophil elastase (NE) are commonly measured markers of inflammation in bronchoalveolar lavage (BAL) fluid from patients with cystic fibrosis. Longitudinal analysis assumes uniform stability during storage, however the effect of extended low-temperature storage on these markers remains unclear. Methods BAL fluid from 104 children with cystic fibrosis was assayed for IL-8 and NE after storage at 4 °C for 7 days and − 80 °C for up to 6 years and compared with the initial assays performed soon after collection. Results IL-8 levels were stable after any measured length of time at − 80 °C or 4 °C. NE levels were stable for 6 months at − 80 °C but decreased beyond that or after 7 days at 4 °C. Conclusions Our data support the stability of IL-8 in BAL stored at − 80 °C for prolonged periods. NE in BAL decreases with storage and should be assayed as soon as practical after collection.