Reference interval and preanalytical properties of serum neurofilament light chain in Scandinavian adults

Abstract

The neurofilament light chain (NfL) is a promising biomarker of neuronal injury which is approaching routine clinical use. With the development of ultra-sensitive technologies, NfL has become measurable in the peripheral blood but the reference interval for serum NfL remains to be established. NfL was measured by a single-molecule array (Simoa™) analysis under internal and external quality control which is established for routine clinical use. Serum samples from 342 reference subjects, 18−87 years were analyzed. The age-partitioned reference interval was established according to Clinical and Laboratory Standards Institute guidelines, an approximation of the upper reference interval limit per 10-year age-groups was performed, and key pre-analytical properties were examined. Serum NfL levels increased 2.9% per year. The non-parametric reference interval for the age groups 18−40, 41−65, and >65 years were 2.8−9.7 ng/L, 4.6 − 21.4 ng/L, and 7.5−53.8 ng/L, respectively. The estimated upper reference interval limits per 10-year intervals corresponded well with the 90% confidence limits of the non-parametric reference interval. The recovery of serum NfL after seven days at room temperature or three freeze-thaw cycles were 93% (95% CI: 89%−97%) and 92% (95% CI: 83%−102%) and levels in serum were only slightly higher than levels in plasma (p < .0001). The study establishes the serum NfL reference interval, provide estimated upper reference intevral limits in 10-year intervals to increase the clinical applicability and uncover pre-analytical properties that make serum NfL feasible for clinical use.

Keywords:

• Neurofilament protein L
• serum
• reference values
• pre-analytical phase
• blood chemical analysis

Acknowledgments

The authors sincerely thank laboratory technician Tine Kusk Jørgensen for her skilled laboratory assistance, head of the outpatient blood sampling unit Marianne N. Holm Simonsen for organizing the collection of blood samples, and the technicians in the blood sampling unit and the blood bank at Aarhus University Hospital for their assistance in collecting the reference samples.

Disclosure statement

None of the authors have any potential conflicts of interest to declare in regard to the present work, but have the following general conflicts of interest: CVBH and CSK has participated in educational activities sponsored by Roche.

The funding organizations played no role in the design of the study, the collection, analysis and interpretation of the results, the writing of the manuscript or the decision to publish.

Additional information

Funding

The study was supported by the Department of Clinical Biochemistry, Aarhus University Hospital. CVBH received a scholarship from the Health Research Fund of Central Denmark Region.