For the discrimination of PD from APDs, the sensitivity of the combined test was higher than that of the tests evaluated individually (91.4% RT-QuIC; 93.9% cNfL; 98.3% combined), whereas the specificity increased compared to that of cNfL assay alone and decreased only slightly compared to that of RT-QuIC test alone (97.5% RT-QuIC; 90.8% cNfL; 95.8% combined, p = 0.047 vs. RT-QuIC alone and p = 0.011 vs. NfL alone) (Table 3). Here, NEFL is linked to Parkinson disease.