It may soon be possible to obtain a highly accurate diagnosis of Alzheimer’s disease by analyzing a sample of spinal fluid. A study released Monday found that a constellation of three substances in the cerebrospinal fluid was present in 90% of people who had been diagnosed with Alzheimer’s.

The test also showed the same markers were found in 72% of people with mild cognitive impairment, considered an early stage of the disease, and in one-third of adults who had no cognitive problems.

Many experts believe that biomarkers in spinal fluid may emerge as the most accurate diagnosis of Alzheimer’s disease. At present, the disease is diagnosed using pencil-and-paper cognitive tests, which are subjective and may be inaccurate. The diagnosis can only be confirmed by examining brain tissue at an autopsy.

Researchers from Belgium analysed 114 older adults who were cognitively normal, 200 who had mild cognitive impairment and 102 who had been diagnosed with Alzheimer’s. They looked for three specific biomarkers, proteins that develop in the brain when the disease is present. A later analysis looking at brain autopsies for confirmation found the test of spinal fluid markers was correct in 64 of 68 cases.

The fact that Alzheimer’s was diagnosed in about one-third […]