Quantification of Tau-A in serum after brain injury: a comparison of two analytical platforms, ELISA and electrochemiluminescence immunoassay

ABSTRACT

Background

Previous studies have indicated the utility of the ADAM10-generated fragment of tau, Tau-A, as marker of neuronal damage. However, the sensitivity of the ELISA-based system was limited.

Objectives

We utilized the extensive dynamic range of electrochemiluminescence compared to colorimetric assessment to improve the sensitivity of the Tau-A assay and investigate Tau-A levels after brain injury.

Methods

We converted the Tau-A competitive ELISA to a competitive electrochemiluminescence-based immunoassay, Tau-A ECLIA, and compared the methods by measuring serum samples in a TBI (n = 40) and a stroke cohort (n = 64).

Results

The Tau-A ECLIA was technically robust. Only 1% of the samples was below the detection limit in the ECLIA compared to 10.6% in the ELISA . Tau-A measured in both assays could discriminate between patients with a TBI and non-trauma controls (ELISA: p = 0.0005, ECLIA: p = 0.0002). The increased dynamic range of the Tau-A ECLIA also allowed discrimination between healthy controls from patients with hemorrhagic (p = 0.0172) and severe ischemic stroke (p = 0.0118) respectively, as well as patients with mild ischemic stroke from severe (p = 0.0445).

Conclusions

The Tau-A ECLIA was characterized by dynamic range compared to the ELISA, which facilitated a better separation between the patient groups. Tau-A warrants further investigation as a neuronal injury associated marker.

KEYWORDS:

• Tau-A fragment
• serum biomarker
• electrochemiluminescence immunoassay
• traumatic brain injury
• stroke

Acknowledgments

We would like to thank Inge Kolding for her technical assistance.

Abbreviations

ADAM10: a disintegrin and metalloprotease 10; AUC: area under the ROC curve; BBB: blood brain barrier; CSF: cerebrospinal fluid; CV: coefficient of variation; CI: confidence interval; ECL: electrochemiluminescence; ECLIA: electrochemiluminescence immunoassay; ELISA: enzyme-linked immunosorbent assay; GCS: Glasgow Coma Scale; LLOD: lower limit of detection; mRS: modified Rankin Scale; MSD: Meso Scale Discovery; NIHSS: National Institute of Health Stroke Scale; ROC: receiver-operating characteristic; Tau-A: ADAM10-generated fragment of tau at Ala152; TBI: traumatic brain injury; ULOD: upper limit of detection

Availability of data and materials

The data that support the findings of this study are available from the corresponding author, KH, upon reasonable request.

Disclosure statement

The authors declare no conflict of interest

Author’s contributions

OT performed the experiments, developed and validated the Tau-A ECLIA assay, analyzed data and wrote the manuscript. SAS, ASW, HKI collected and provided the serum samples for the stroke study. SAS, HKI, MAK and KH reviewed and edited the manuscript. The final version of the manuscript was read and approved by all authors.

Additional information

Funding

This project has received funding from the European Union’s Horizon 2020 Marie Skłodowska-Curie Innovative Training Networks-European Training Networks BBDiag project under grant No. H2020-MSCA-ITN-2016 721281. The Danish Research Foundation (“Den Danske Forskningsfond”) also supported this work. The funding parties had no role in the design of the study and collection, analysis, and interpretation of data and in writing the manuscript.