Table 6.

Summary of analytical validation of the LDT version of the NfL assay.

Characteristic	Serum	Plasma	CSF
Reportable range	3.9–500 pg/mL	4.9–477 pg/mL (K2 EDTA) 2.4–549 pg/mL (Lithium Heparin)	85.5–25,700 pg/mL
Reproducibility	4.9–8.4%	7.7–18.1% (K2 EDTA) 3.5–16.3% (Lithium Heparin)	4.0–16.5%
Method comparison	Quanterix vs Atellica® platform: Avg Quantitation Difference: −8%; Pearson correlation: R = 0.995 ADVIA Centaur XP vs. Atellica® platform: Average Quantitation Difference: 9%; Pearson correlation: R = 1.0	Tested for serum only; specimen equivalence was established based on precision and accuracy (CLSI EP35)	Quanterix vs. Atellica® platform: Avg Quantitation Difference: −29%; Pearson correlation: R = 0.994 ADVIA Centaur XP vs Atellica® platform: Average Quantitation Difference: −13.2%; Pearson correlation: R = 0.996
Specimen handling	NfL is stable under the following conditions: •Up to 6 freeze/thaw cycles •Up to 1 week at room temperature •Up to 2 weeks refrigerated •Frozen at −20°C for 1 year •Frozen at −80°C for 1 year	NfL is stable under the following conditions: •Up to 6 freeze/thaw cycles •Up to 1 week at room temperature •Up to 2 weeks refrigerated •Frozen at −20°C: 3 months (K2 EDTA) and 6 months (Lith Hep) •Frozen at −80°C: 6 months (K2 EDTA) and 1 year (Lith Hep)	NfL is stable under the following conditions: •Up to 6 freeze/thaw cycles •Up to 1 week at room temperature •Up to 1 week refrigerated •Frozen at −20°C for 3 months •Frozen at −80°C for 1 year
Interfering substances	Interference testing for endogenous substances. Assay interference was not observed in samples with the following substances and concentrations:•Hemoglobin below 500 mg/dL •Direct bilirubin below 60 mg/dL •Indirect bilirubin below 40 mg/dL •Albumin below 6 g/dL •Triglycerides below 2,000 mg/dL •RF below 193 U/mL •Biotin below 3,500 ng/mL •Neurofilament Heavy Chain below 1000 pg/mL •Neurofilament Medium Chain below 1000 pg/mL	Tested for serum only; specimen equivalence was established based on precision and accuracy (CLSI EP35)	Tested for serum only; specimen equivalence was established based on precision and accuracy (CLSI EP35)
Drug interference	Drug interference testing was performed using the following drugs used to treat patients with Alzheimer's and MS:•Donepezil •Rivastigmine •Memantine •Galantamine •Citalopram •Mirtazapine •Sertraline •Bupropion •Duloxetine •Imipramine •Ibuprofen •Siponimod •Acetaminophen •Aspirin •Beta interferon 1a •Beta interferon 1b •Fingolimod •Dimethyl fumarate •Teriflunomide •Ocrelizumab •Mitoxantrone •Caldribine •Alemtuzumab •Glucose •Drug interference (±20%) was observed in the presence of Mitoxantrone at concentrations >0.113 mg/dL.	Tested for serum only; specimen equivalence was established based on precision and accuracy (CLSI EP35)	Tested for serum only; specimen equivalence was established based on precision and accuracy (CLSI EP35)

CLSI, clinical and laboratory standards institute; CSF, cerebrospinal fluid; MS, multiple sclerosis; NfL, neurofilament light chain.