Serum neurofilament light chain as an early diagnostic biomarker for critical illness polyneuropathy

BACKGROUND: Critical illness polyneuropathy (CIP) commonly occurs in critical care unit (CCU) patients, but timely diagnosis can be challenging. Therefore, new biomarkers, such as serum neurofilament light chain (sNfL), could help to improve early identification of patients with this condition.METHODS: CIP was diagnosed or excluded with neurological assessment and nerve conduction measurement in a prospective study of CCU patients. sNfL and secondary predictors for neuropathy (neuron-specific enolase (NSE), S100, folic acid, and vitamin B12) were measured at admission. Cases and controls were compared regarding the predictors.RESULTS: Nineteen patients met the inclusion criteria. CIP was considered definitely or most likely present in seven (37%, cases) and definitely or most likely absent in 12 individuals (63%, controls). At admission, sNfL levels were sig-nificantly higher in the cases than in the controls: 405 (IQR 77 to 835) vs. 27 (IQR 12 to 90) pg/mL; difference of medians 375, 95% confidence interval [14, 736], pg/mL; P=0.04. We found no significant differences regarding the secondary predictors at baseline. Cases had longer durations of CCU stay (median 19 (IQR 11 to 44) vs. 8 (IQR five to ten) and increased mortality (57% vs. 33% deceased) compared to controls.CONCLUSIONS: Levels of serum neurofilament light chain are higher in patients who develop CIP soon after CCU admission and might be helpful in identifying those individuals early.