Evaluation and limitations of the novel chemiluminescent enzyme immunoassay technique for measuring total tau protein in the cerebrospinal fluid in patients with human prion disease: a 10-year prospective study (2011–2020) (preprint)

ABSTRACT

Background: Recently, the investigation of cerebrospinal fluid (CSF) biomarkers for diagnosing human prion diseases (HPD) has garnered significant attention. Reproducibility and accuracy are paramount in biomarker research, particularly in the measurement of total tau (t-tau) protein, which is a crucial diagnostic marker. Given the global impact of the coronavirus disease pandemic, the frequency of measuring this protein using one of the world's fully automated assays, chemiluminescent enzyme immunoassay (CLEA), has increased. At present, the diagnosis and monitoring of neurological diseases mainly rely on traditional methods, but their accuracy and responsiveness are limited.there is a limited knowledge on the accuracy of CLEA in Tau measurements. We aimed to measure t-tau protein using CLEA and to elucidate its merits and limitations. Methods: We analysed CSF samples obtained from 91 patients with rapidly progressive dementia using ELISA and CLEA. Additionally, we used western blotting to detect the presence of 14-3-3 protein and employed real-time quaking-induced conversion (RT-QuIC) assays to analyse the same set of samples. Furthermore, we examined the correlation coefficient between ELISA and CLEA results in a subset of 30 samples. Moreover, using CLEA, we evaluated the diurnal reproducibility, storage stability, dilutability, and freeze-thaw effects in three selected samples. Results:Among the 91 patients, a total of 45 (22 men and 23 women) tested positive for HPD in the RT-QuIC assay. In contrast, all CSF samples from the remaining 46 patients without HPD (23 men and 23 women) tested negative in the RT-QuIC assay. Both ELISA and CLEA showed perfect sensitivity and specificity (100%) in measuring t-tau protein levels. Furthermore, there was a strong correlation coefficient (R² = 0.9363) between ELISA and CLEA results. However, despite its advantages, CLEA analysis exhibited instability for certain samples with t-tau protein levels exceeding 2,000 pg/mL, leading to low reproducibility during dilution analysis. Conclusions: Our findings indicate that CLEA outperforms ELISA in terms of diurnal reproducibility, storage stability, and freeze-thaw effects. However, ELISA demonstrated superior performance in the dilution assay. Therefore, it is imperative to develop innovative approaches for the dilution of biomarker samples for CLEA measurements during clinical trials.