Summary: Measuring the level of neurofilaments in the blood may be a reliable biomarker for the early diagnosis of ALS.
Source: University of Gothenburg
Blood tests may enable more accurate diagnosis of ALS at an earlier stage of the disease. As described in a study by researchers at University of Gothenburg and Umeå University, it involves measuring the blood level of a substance that, as they have also shown, varies in concentration depending on which variant of ALS the patient has.
The study, published in Scientific Reports, include Fani Pujol-Calderón, postdoctoral fellow at Sahlgrenska Academy, University of Gothenburg, and Arvin Behzadi, doctoral student at Umeå University and medical intern at Örnsköldsvik Hospital, as shared first authors.
Currently, it is difficult to diagnose amyotrophic lateral sclerosis (ALS), the most common form of motor neuron disease, early in the course of the disease. Even after a prolonged investigation, there is a risk of misdiagnosis due to other diseases that may resemble ALS in early stages. Much would be gained from earlier correct diagnosis and, according to the researchers, the current findings look promising.
Neurofilaments—proteins with a special role in the cells and fibers of nerves—are the substances of interest. When the nervous system is damaged, neurofilaments leak into the cerebrospinal fluid (CSF) and in lower concetrations in blood compared to CSF.
In their study, scientists at Umeå University and the University Hospital of Umeå, as well as at the University of Gothenburg and Sahlgrenska University Hospital in Gothenburg, demonstrated that CSF and blood levels of neurofilaments can differentiate ALS from other diseases that may resemble early ALS.
More sensitive methods of analysis
Compared with several other neurological diseases, previous studies have shown higher concentrations of neurofilaments in CSF in ALS. Measuring neurofilament levels in the blood has previously been difficult since they occur at much lower concentrations compared to CSF. In recent years, however, new and more sensitive analytical methods have generated new scope for doing so.
The current study shows a strong association, in patients with ALS, between the quantity of neurofilaments in the blood and in CSF. The study is based on blood and CSF samples collected from 287 patients who had been referred to the Department of Neurology at the University Hospital of Umeå for investigation of possible motor neuron disease. After extensive investigation, 234 of these patients were diagnosed with ALS. These had significantly higher levels of neurofilaments in CSF and blood compared to patients who were not diagnosed with ALS.
Differences among various subgroups of ALS were also investigated and detected. Patients whose pathological symptoms started in the head and neck region had higher neurofilament concentrations in the blood and worse survival than patients whose disease onset began in an arm or a leg. The study has also succeeded in quantifying differences in blood levels of neurofilaments and survival for the two most common mutations associated to ALS.
“Finding suspected cases of ALS through a blood test opens up completely new opportunities for screening and measuring neurofilaments in blood collected longitudinally enables easier quantification of treatment effects in clinical drug trials compared to longitudinal collection of CSF. Finding ALS early in the disease course may facilitate earlier administration of pharmaceutical treatment, before the muscles have atrophied,” Arvin Behzadi says.
ALS is a neurodegenerative syndrome that leads to loss of nerve cells in both the brain and the spinal cord, resulting in muscle weakness and atrophy. Most of these patients die within two to four years after the symptom onset, but roughly one in ten survive more than ten years after the symptoms first appeared.
Several genetic mutations have been associated to ALS. At present, there is no curative treatment. Nevertheless, the current drug available has been shown to prolong the survival in some ALS patients if it is administered in time.
Neurofilaments can differentiate ALS subgroups and ALS from common diagnostic mimics
Delayed diagnosis and misdiagnosis are frequent in people with amyotrophic lateral sclerosis (ALS), the most common form of motor neuron disease (MND). Neurofilament light chain (NFL) and phosphorylated neurofilament heavy chain (pNFH) are elevated in ALS patients.
We retrospectively quantified cerebrospinal fluid (CSF) NFL, CSF pNFH and plasma NFL in stored samples that were collected at the diagnostic work-up of ALS patients (n = 234), ALS mimics (n = 44) and controls (n = 9). We assessed the diagnostic performance, prognostication value and relationship to the site of onset and genotype. CSF NFL, CSF pNFH and plasma NFL levels were significantly increased in ALS patients compared to patients with neuropathies & myelopathies, patients with myopathies and controls.
Furthermore, CSF pNFH and plasma NFL levels were significantly higher in ALS patients than in patients with other MNDs. Bulbar onset ALS patients had significantly higher plasma NFL levels than spinal onset ALS patients. ALS patients with C9orf72HRE mutations had significantly higher plasma NFL levels than patients with SOD1 mutations. Survival was negatively correlated with all three biomarkers.
Receiver operating characteristics showed the highest area under the curve for CSF pNFH for differentiating ALS from ALS mimics and for plasma NFL for estimating ALS short and long survival. All three biomarkers have diagnostic value in differentiating ALS from clinically relevant ALS mimics. Plasma NFL levels can be used to differentiate between clinical and genetic ALS subgroups.