A metagenomic next-generation sequencing (mNGS) test of cerebrospinal fluid samples designed to detect CNS infections can also pick up difficult-to-diagnose tumours in the brain and spinal cord, US researchers say.

The test could help distinguish between various autoimmune disorders, infections and malignancies that can all present as meningoencephalitis, the authors say.

Analysis of data from two case-controlled studies with a total of 130 patients found that mNGS – which can be used to look for gene copy number variations indicating aneuploidy – had a sensitivity of 75% and a specificity of 100% in detecting genetic evidence of a malignancy, according to the results published in JAMA Neurology.

“This study builds on earlier work where we looked at DNA and RNA in the spinal fluid to see if there were infections in the CNS, which led us to a clinically validated test to look for mystery infections that affect the brain and spinal cord,” said the study’s lead author, Dr Wei Gu, who was working at the University of California, San Francisco (UCSF), when that research was done.