Scientists discovered liquid biopsy marker for schizophrenia spectrum disorders

When we go to the hospital or have a medical checkup, we basically have a blood test to get blood biochemical indicators like blood glucose, blood lipids, liver, and kidney function. These indicators, also known as biomarkers, can reflect organ and body function and status.

A group of researchers led by Dominique Endres of the University of Freiburg in Germany recently published an important study on diagnostic biomarkers for schizophrenia spectrum disorder (SSD, also known as schizophrenia) in Schizophrenia Bulletin, a top journal in the field of psychiatry. They found significantly elevated levels of neurofilament mid-chain protein (NFM) in the cerebrospinal fluid of SSD patients compared to controls, which is expected to be a candidate biomarker for SSD.

SSD is a common and serious psychiatric disorder in which patients often exhibit a variety of emotional, behavioral and cognitive abnormalities consisting of delusions, hallucinations, reduced emotional expression, and cognitive impairment.

As of today, the exact cause of the pathogenesis of SSD remains unclear. Some theories suggest that SSD is a neurodevelopmental disorder that is influenced by genetics and the environment. Some scholars also classify SSD as a neurodegenerative disease called "early onset dementia", which refers to the early onset of cognitive decline that progressively worsens with age.

Studies from imaging, autopsy, and biomarkers have shown that patients with SSD have similar pathological changes as patients with other neurodegenerative diseases, including disrupted neuronal, synaptic, and axonal integrity.

Therefore, the Endres team wanted to know if biomarkers commonly used in other neurodegenerative diseases, such as Alzheimer's disease (AD), were also altered in the cerebrospinal fluid of SSD patients.

The researchers based this study on cerebrospinal fluid samples from 100 SSD patients from a previous study. All of these SSD patients were at least 18 years old, and lumbar puncture was part of their routine diagnostic testing. There were 60 females and 40 males among them, with a mean age of 33.72 years.

These patients were admitted to the hospital and diagnosed by experienced psychiatrists according to ICD-10 criteria. 56% of these patients had paranoid schizophrenia, and 30% had schizoaffective disorder. In terms of illness duration, 58% of patients were chronic or relapsing, while 42% were first-time patients. In addition, as a control group, the Endres team collected cerebrospinal fluid samples from 39 patients (33 female and 6 male; mean age 34.62 years) diagnosed with idiopathic intracranial hypertension (IIH), a non-teratogenic central nervous system disorder that necessitates repeating lumbar puncture for cerebrospinal fluid for diagnosis and treatment. The control group's patients had no history of psychiatric disorders or psychotropic drug use.

The Endres team found that NFM concentrations were significantly higher and p-tau protein concentrations were significantly lower in the cerebrospinal fluid of patients with SSD compared to controls by measuring multiple neurodegenerative markers in the cerebrospinal fluid, with no significant change in the ratio of Aβ. In addition, they observed a significant interaction between different test groups and gender on NFM concentrations.

To further clarify the alterations in neurodegenerative markers across SSD subtypes, gender, and disease duration, the Endres team performed four subgroup analyses. Specifically, hallucinatory delusional SSD and schizo-affective SSD were compared to controls, hallucinatory delusional compared to schizo-affective, and chronic recurrent patients compared to first-time patients.

They only discovered statistically significant variations in gender between patients with hallucinatory delusional SSD and controls, not in age differences across the other categories.

Additionally, they discovered that p-tau protein was significantly different only between hallucinatory delusional SSD patients and controls, whereas NFM was considerably higher in the CSF fluid of both hallucinatory delusional and schizo-affective SSD patients compared to controls. NFM concentration in the cerebral fluid of SSD patients was positively connected with NFL, p-tau protein, total-tau protein concentrations, and age, the Endres team discovered using correlation analysis. Correlation analysis also revealed significant correlations between NFL and NFM concentrations in cerebrospinal fluid and total protein concentrations and cerebrospinal fluid/serum albumin ratio (QAlb) in patients with SSD.

The current diagnostic criteria for SSD place a greater emphasis on patient behavior assessment and frequently involve patient self-assessment, which is very subjective and not helpful for early diagnosis or efficacy evaluation. The scientific reliability of SSD diagnosis will be significantly increased if optimal biomarkers for SSD can be discovered.

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