If you just go by the headlines, you'd think that the science of biomarkers had taken another hit. "Alzheimer's tests using pen and paper still the best," says the Booster Shots blog in the Los Angeles Times; "Biomarkers Flunk Alzheimer's Test," says MedPage Today. But if you read the articles, and the paper in the Archives of General Psychiatry on which they are based, you'd see that the proverbial apples are being compared with oranges. Biomarkers may, indeed, be best for early, presymptomatic Alzheimer's disease, while old-fashioned pen-and-paper cognitive tests are not only biomarkers for the degenerative neurological disease, but are used to diagnose it in the first place.
The authors took a close look at 116 people with mild cognitive impairment who later developed Alzheimer's, along with 204 who did not develop the disease and 197 cognitively healthy people. They ran the whole battery of tests on them, including pen-and-paper tests, spinal fluid and blood tests, plus brain scans. They found that two cognitive tests more-accurately predicted whether a patient would develop Alzheimer's than did any changes in biomarkers.
However, the study's authors added that biomarkers "may be most informative in very early prodromal stages, a perspective that has been incorporated into proposed diagnostic criteria for preclinical AD." They continue: "One might argue that the use of cognitive markers in this context is a tautology because they are used in the diagnosis of [Alzheimer's disease] itself." So, they say, cognitive markers offer an advantage over biomarkers because they cost less and take up less time, among other things, they also are more likely to predict Alzheimer's simply because measurable cognitive impairment is a criteria for diagnosing the disease in the first place.
This still leaves room for biomarkers as a predictor before cognitive impairment is measurable by pen-and-paper tests.