This test is for the quantification of NfL in plasma to assist in the clinical assessment of neurological disorders. NfL is a nonspecific biomarker for axonal degeneration; elevated NfL levels are associated with a range of neurological disorders including AD, ALS, MS, FTD, and TBI.


Test code:


Abbreviations, alternative names:

Plasma NfL


Chemiluminescent enzyme immunoassay (CLEIA)


Laboratory developed test (LDT)


Specimen type:

EDTA plasma

Minimum volume:

0.5 mL

Preferred volume:

5 mL

Rejection criteria:

Grossly hemolytic, icteric, or lipemic. If the sample arrives at room temperature

Our offices are only able to receive samples Mon-Fri, so samples must be shipped Mon-Thur. Samples arriving over the weekend may need to be re-drawn.


NfL is very sensitive to temperature and freeze/thaw cycles. Time at room temperature should be minimized.

Specimen collection:

Overnight fasting recommended
Draw blood in K2 EDTA tubes (lavender top).
Invert 8 times to ensure complete mixing

Specimen handling:

Centrifuge EDTA tubes at 1800 - 2200 x g for 10-15 minutes
Draw off plasma into Aliquot tubes with pipette, ensuring not to take gel or RBC (middle/bottom layers)
Immediately store Aliquot tubes in refrigerator (2°C - 8°C) until shipping

Specimen storage:

Plasma samples must either be refrigerated and shipped chilled within 24 hours of collection, or frozen and shipped on dry ice


Testing frequency:

Once a week

Turnaround time:

3-5 days

Reference range:

Age group
20 – 29 (≤ 8.4 ng/L)
30 – 39 (≤ 11.4 ng/L)
40 – 49 (≤ 15.4 ng/L)
50 – 59 (≤ 20.8 ng/L)
60 – 69 (≤ 28.0 ng/L)
70 – 79 (≤ 37.9 ng/L)
≥ 80 (≤ 51.2 ng/L)


Laboratory developed test (LDT)

Additional Information

  • This is a laboratory developed test, its performance was determined by Neurocode USA Inc. It has not been cleared or approved by the Food and Drug Administration.
  • Elevated NfL is not a disease specific factor and may be caused by a neurodegenerative disease or traumatic brain injury. Results should be used in conjunction with clinical signs and symptoms.
  • NfL levels measured in the evening may be more than 10% lower than those measured in the morning (Benedict et al 2020).
  • Higher levels of NfL can occur in patients with a history of stoke, atrial fibrillation, myocardial infarction, chronic kidney disease, pregnancy, and diabetes. Lower levels may be found in person who are obese (BMI ≥ 30) (Syrjanen et al 2022).