There is currently no diagnostic test for distinguishing between PD and APD, but NfL is an emerging biomarker with high diagnostic accuracy for ADP, but not PD, when cerebrospinal fluid (CSF) levels are elevated. However, several barriers to obtaining CSF exist, including the requirement for a lumbar puncture and patient unease about undergoing this procedure.
Oskar Hansson, MD, PhD, from Lund University and Skkar University Hospital in Sweden, and colleagues with the Swedish BioFINDER study developed an ultrasensitive single-molecule array immunoassay for NfL that correlates blood levels with CSF levels. The researchers evaluated whether blood concentrations of NfL were elevated in patients with APD vs patients with PD and healthy control patients in cohorts recruited from Lund and London, United Kingdom.
A total of 278 patients were recruited in the Lund cohort, and 117 patients were enrolled in the London cohort. Patients with APD included those with progressive supranuclear palsy, multiple system atrophy, and corticobasal syndrome.
Blood concentrations of NfL strongly correlated with CSF NfL in both cohorts (P <.001 for both comparisons).
Patients with APD had significantly higher levels of blood NfL than patients with PD or healthy control patients (P <.001 for all comparisons). Among patients with early-stage disease, defined as disease onset ≤3 years, blood NfL was increased in all APD types compared with PD (P < .001 for all comparisons).
Blood NfL levels were found to have high diagnostic accuracy for differentiating APD from PD (area under the curve, 0.91), which is similar to that of CSF NfL levels.
According to Dr Hansson, elevated levels of blood NfL in a patient with parkinsonism could be an indicator that the patient may have an APD. “However, the results of NfL is only one piece of the puzzle, and the neurological examination, patient history, and brain imaging will still be very important for diagnosis,” he told Neurology Advisor.
Dr Hansson also noted that although blood NfL is increased in progressive supranuclear palsy, multiple system atrophy, and corticobasal syndrome, it cannot differentiate between the different types of APD. “We will need more specific biomarkers in the future that can separate these APDs from each other,” he said.
Hansson O, Janelidze S, Hall S, et al. Blood-based NfL: a biomarker for differential diagnosis of parkinsonian disorder [published online February 8, 2017]. Neurology. doi: 10.1212/WNL.0000000000003680
This article originally appeared on Neurology Advisor