The use of cerebrospinal fluid (CSF) biomarkers in the early detection of Alzheimer disease (AD) has grown as the diagnostic criteria for AD have evolved over the past few years. The International Working Group for New Research Criteria for the Diagnosis of AD mandates the use of beta-amyloid (Aβ) and tau biomarkers via neuroimaging and CSF testing, and the National Institute on Aging–Alzheimer’s Association takes a similar stance in its criteria. Both sets of criteria recognize the concept of a preclinical stage AD that may be recognized before the onset of dementia and underscore the need for biomarkers to aid in early AD diagnosis.1

Previous research indicates that psychiatric disorders may be risk factors for AD or part of its prodrome, and a new multicenter, prospective observational cohort study sought to determine the utility of CSF biomarkers for AD in diagnosing psychiatric patients.2 “AD CSF biomarkers are the only markers that reflect the AD neuropathological lesions associating tau and amyloid β,” and positive “CSF biomarkers imply that patients have AD brain lesions with or without clinically detectable AD features,” wrote the authors in their paper that appeared in Alzheimer’s Research & Therapy. Theirs is the first study to examine the role of CSF biomarkers in the diagnosis of patients with cognitive symptoms and psychiatric disorders in routine daily clinical practice.

Clinicians at 29 memory clinics in France completed anonymous questionnaires regarding 957 patients with initial diagnoses of psychiatric disorders who underwent CSF biomarker testing. Prior to obtaining the testing results, the clinicians–consisting of 61 neurologists, 65 geriatricians, and 2 psychiatrists–indicated their diagnosis, level of diagnostic confidence, and treatment details. Results show an initial diagnosis of a psychiatric disorder in 69 of the patients (anxiety and/or depression in approximately 62% of this group, and bipolar disorder, psychosis or “other” in the remaining cases), 20.2% of whom were found to have a CSF AD profile. An intermediate CSF profile was found in 7.2% of patients, and 72.4% had a non-AD profile. Approximately 18.8% of patients ultimately received a diagnosis of AD; in these patients, psychiatric symptoms appeared later in life, and there was a shorter delay between the onset of psychiatric symptoms and cognitive decline.

“The impact of CSF biomarker results was clear with regard to the magnitude of changed diagnoses, with treatment modification in more than 30 % of cases,” and there was a significant improvement in the clinicians’ diagnostic confidence, according to the paper. Distinguishing between psychiatric disorders and AD is crucial because of the differing prognosis and management of the two. For example, some types of treatment–such as anticholinergic medications–are commonly used in psychiatric disorders but are not recommended for use in neurodegenerative diseases. The “use of biomarkers improves the precision of the diagnosis and allows provision of better information and medical care to the patient as well as more specific supportive care for the patient’s relatives,” the authors concluded.

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1. Cicognola C,Chiasserini D, Parnetti L. Preanalytical confounding factors in the analysis of cerebrospinal fluid biomarkers for Alzheimer’s disease: the issue of diurnal variation. Front Neurol. 2015; 6: 143.

2. Paquet C, Magnin E, Wallon D, et al. Utility of CSF biomarkers in psychiatric disorders: a national multicentre prospective study. Alzheimers Res Ther. 2016; 8:27.