Diagnostic value of cerebrospinal fluid tau and real⁃time quaking⁃induced conversion in sporadic Creutzfeldt⁃Jakob disease

Objective To explore the diagnostic value of cerebrospinal fluid (CSF) biomarkers, total tau protein (t‑tau), phosphorylated tau protein 181 (p‑tau181) and real‑time quaking‑induced conversion (RT ‑QuIC) in sporadic Creutzfeldt‑Jakob disease (sCJD). Methods A retrospective study was conducted on 30 patients diagnosed with probable sCJD at Huashan Hospital, Fudan University from April 2020 to November 2022, serving as the sCJD group. Meanwhile, 25 patients diagnosed with rapidly progressive Alzheimer's disease (AD) and 23 patients diagnosed with autoimmune encephalitis (AE), matched for gender and age with the sCJD group, were selected as the AD group and AE group, respectively. CSF t‑tau, p ‑ tau181 and t‑tau/p‑tau181 ratio were collected from the 3 groups. The auxiliary examination data of the sCJD group, including typical manifestations of electroencephalography (EEG) and head MRI, as well as RT‑ QuIC results, were collected with emphasis. Results There were statistically significant differences in CSF t‑tau (χ2 = 38.247, P = 0.000), p‑tau181 (χ2 = 22.855, P = 0.000) and t‑tau/p‑tau181 ratio (χ2 = 43.780, P = 0.000) among 3 groups. Further pairwise comparisons revealed that the t‑tau in the sCJD group was higher than that in the AD group (Z = ‑ 4.392, P = 0.000) and AE group (Z = ‑ 5.852, P = 0.000); the p‑tau181 in the AD group was higher than that in the sCJD group (Z = 2.830, P = 0.014) and AE group (Z = 4.758, P = 0.000); the t‑tau/p‑tau181 ratio in the sCJD group was higher than that in the AD group (Z = ‑ 6.601, P = 0.000) and AE group (Z = ‑ 3.339, P = 0.003), and the t‑tau/p‑tau181 ratio in the AE group was higher than that in the AD group (Z = ‑ 2.984, P = 0.009). Among the 30 patients in the sCJD group, 70% (21/30) exhibited abnormal MRI findings in the brain, all displaying the typical cortical "lace sign"; 40% (12/30) showed typical triphasic waves on EEG. In the sCJD group, 7 cases underwent CSF RT ‑ QuIC, and pathogenic prion protein was detected in 5 patients. Conclusions Elevated CSF t‑tau and t‑tau/p‑tau181 ratio, as well as positive RT‑QuIC results, hold certain diagnostic value for sCJD.