There is currently no physiological diagnosis for schizophrenia. The only two ways to diagnose the disease are to rely on a psychological evaluation, where the disease may be mistaken for another ailment, or to take brain samples during an autopsy and look for a specific biomarker, after the person has died.

But new research at Tel Aviv University showed that samples taken from a living person can confirm the psychological diagnosis of schizophrenia with physical evidence.

Researchers know that a certain microRNA, MiR-382, suppresses gene expression (rather than encouraging gene expression like normal RNA) and is a telltale sign of the disease. The problem is that because the microRNA resides in the neurons of the brain, to test for its presence researchers must take brain samples immediately after death. This cannot be done to confirm a diagnosis in a living patient.

But now researchers from Israel have found that when taking neuron samples from inside of the nose, only in patients diagnosed with schizophrenia do they find detectable levels of the specific microRNA.

The scientists took cells from inside the noses of seven patients diagnosed with schizophrenia and seven participants who did not have the disease. After culturing the cells in a lab, they found that only those cells from patients diagnosed with schizophrenia expressed the specific microRNA.

"We were able to narrow down the microRNA to a differentially expressed set, and from there down to a specific microRNA which is elevated in individuals with the disease compared to healthy individuals," explaind Dr. Noam Shomron, lead researcher on the project.

The researchers concluded that taking biopsy samples from inside patients' noses may be a useful diagnostic tool for schizophrenia. 

The technique may also help diagnose other diseases, such as Alzheimer's disease, where the only true way to confirm it is by autopsy and analysis of the brain. Because many Alzheimer's patients lose their sense of smell before memory issues develop, the nose may be a "canary in the mineshaft" for the confirmation of a variety of disease diagnoses based on psychological symptoms.

The research was published in the journal Neurobiology of Disease and can be found here.