The Enhanced Liver Fibrosis (ELF) Panel: Analyte Stability Under Common Sample Storage Conditions Used in Clinical Practice.

BACKGROUND The enhanced liver fibrosis (ELF) blood test has recently been recommended by the National Institute for Health and Care Excellence to test for advanced fibrosis in nonalcoholic fatty liver disease. The ELF test involves calculating a score from the concentrations of serum biomarkers: tissue inhibitor of matrix metalloproteinases-1 (TIMP-1), aminoterminal propeptide of procollagen type III (P3NP), and hyaluronic acid (HA). Blood samples for the ELF score are often acquired in primary care and may be stored before analysis. However, the effect of preanalytical storage on the ELF test is not known. METHODS We conducted experiments to assess the stabilities of the ELF score, P3NP, HA, and TIMP-1 under medium- to long-term storage at -80 °C, repeated freeze-thawing, and refrigeration at 4 °C for days. RESULTS Mean TIMP-1 concentrations increased during medium- to long-term storage (+16.5%) and refrigeration (+4.9%), but were stable during freeze-thawing. Mean P3NP concentrations were stable under medium- to long-term storage, but increased during refrigeration (+7.4%) and freeze-thawing (+9.3%). Mean HA concentrations decreased during medium- to long-term storage (-12.3%) but were stable during refrigeration and freeze-thawing. Despite changes in biomarker concentrations, the changes in the mean ELF score were not clinically significant and not >0.1 U (0.7%). CONCLUSIONS The ELF score was stable, with no clinically significant changes under common storage conditions. These findings demonstrate that the ELF score is robust in situations where analysis may be delayed.