Neurological Disorders

Development of Assaying Plasma TDP-43 Utilizing Immunomagnetic Reduction

Abstract

Shieh-Yueh Yang*, Heui-Chun Liu, Chin-Yi Lin, Ming-Jang Chiu, Ta-Fu Chen, Chin-Hsien Lin and Hsin-Hsien Chen

TDP-43 is a promising biomarker for frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). However, studies on TDP-43 in human biofluid are rare. In this work, the authors utilized an ultrasensitive technology, called immunomagnetic reduction (IMR), to develop the reagent for assaying TDP-43. The preclinical performance characteristics of the TDP-43 reagent, such as the standard curve, detection limits, assay linearity, dilution recovery range, assay reproducibility, spike recovery, reagent stability, and interference tests, were explored according to the CLSI guidelines. Plasma samples from normal controls (NC, n = 27) and from patients with frontotemporal dementia (FTD, n = 9), Alzheimer’s disease (AD, n = 34) and Parkinson’s disease (PD, n = 10) were collected for TDP-43 assays using the IMR TDP-43 reagent. The low-detection limit of assaying TDP-43 was 0.68 fg/ml, and the upper-detection limit was 100 pg/ml. There was no significant interference effect when assaying TDP-43 mixed with hemoglobin, bilirubin, intralipid, albumin, etc. The FTD patients had significantly higher levels of plasma TDP-43 (0.419 ± 0.193 pg/ml ) compared to the NC subjects (0.163 ± 0.097 pg/ml ), AD patients (0.165 ± 0.082 pg/ml ) and PD patients (0.069 ± 0.068 pg/ml ). Through analysis of the ROC curve, the cut-off value of plasma TDP-43 for discriminating FTD from the other patient groups was 0.237 pg/ml, which resulted a clinical sensitivity of 0.889 and a specificity of 0.831. These results demonstrate the feasibility of assaying plasma TDP-43 to specifically identify FTD.