Sabine Bahn is a neurobiologist, psychiatrist and director of the Cambridge Centre for Neuropsychiatric Research at the University of Cambridge, UK. Her research focuses on trying to understand the biological basis of severe psychiatric disorders such as schizophrenia and bipolar disorder. Within the EU-funded project SchizDX, Bahn and colleagues aimed at developing a blood-based diagnostic tests for these disorders. Here, Sabine Bahn talks to youris.com about her ongoing quest for biomarkers that could make the diagnosis of schizophrenia more objective and enable earlier and better treatment of patients.

What was the top-level vision of the project?
Our aim is to improve the diagnosis and disease management of people who suffer from severe mental illness. At present, the treatment is a trial and error approach. About 30% to 40% of patients do not respond to first-line treatment. Blood biomarkers that predict drug response would reduce the risk of non-response, reduce the time to recovery and improve disease outcome.

Another problem is misdiagnosis. Current clinical diagnosis is based on a clinical interview. However, there are no specific symptoms for a given psychiatric disorder. This means that misdiagnosis and delay in diagnosis is a common problem. Biomarker based blood tests may help to develop objective tests like those already widely used in the field of oncology.

Why is it important to have an objective blood test?
In my view and experience as a psychiatrist, it is the patients who want to know the biological basis of their disease. A lot of people do not want to talk about their psychiatric symptoms, for example, that they are hearing voices. A blood test can help to explain the disorder in a rational way. Patients may feel more comfortable with a biological disease model. However, the blood-based test would be in addition to the conventional diagnostic, based on an interview and analysis of family history.

How do you envisage the biomarker-based test to be used in practice?
Psychiatric disorders are not easily diagnosed. GPs often see their patients for too short a time to be able to diagnose depression or schizophrenia. We envisage the test to be applied as an aid for GPs. For example, a patient sees the GP and may complain of feeling anxious, exhausted and being preoccupied with negative thoughts. Or they may even complain of somatic symptoms such as unexplained headaches and pains. All these symptoms are frequently associated with a depressive disorder, but also with many other diseases.

If the GP has a suspicion that the patient suffers from depression, they could collect a blood sample and send the blood to our diagnostics company for analysis alongside a short patient questionnaire. The GP would then, within four to five days, obtain a report, which will give a probability of the patient suffering from depression. If the patient tests positive, the GP will then, hopefully, also obtain a recommendation for antidepressant treatment. That is, which class of antidepressant the patient is most likely to respond to.

If the patient does not test positive, the GP may wait before prescribing antidepressants, as many mild mood disorders are self-limiting. In more difficult cases, the patient would be referred to the psychiatrist.

What are the limitations of your approach?
It is not likely that a single biomarker will give us the information we need to diagnose or distinguish patients suffering from different forms of a mental disorder. Thus we need to develop a complex biomarker assay system, which is more costly. This is why we have partnered with a major diagnostics company, which has the resources to take our findings to the next level.

What are your hopes for future development?
We have some encouraging results for diagnosis and prognosis and sub-stratification of schizophrenia and mood disorder patients. So far, we were able to show that a number of biomarker changes are reproducible across several patient cohorts obtained from different countries. We now need to validate these findings in a prospective clinical trial. I hope that at least one test will be launched within the next 18 months.