Usefulness of Cerebrospinal Fluid Alzheimer's disease biomarkers in older patients: Evidence from a national multicenter prospective study.

Background: The use of cerebrospinal (CSF) biomarkers in the diagnosis of Alzheimer's disease (AD) has been gaining interest in clinical practice. Although their usefulness has been demonstrated, their potential value in older patients remains debated.

Objectives: To assess whether knowledge of the results of CSF AD biomarkers was associated with the same gain in diagnostic confidence in older adults > 80 than in younger patients.

Design: Prospective multicenter study, including memory clinics physicians who completed a two-part questionnaire for all their patients addressing the requirement for assessment of Alzheimer's disease biomarkers in CSF proposed as part of routine care during the study period.

Setting: 30 secondary or tertiary memory clinics in France.

Measurements: Clinicians indicated their diagnosis hypothesis and an estimate of their diagnostic confidence [scale 1-10]. Receiver operating characteristic (ROC) analysis, including the calculation of the area under the curve (AUC), was conducted using logistic regression to evaluate the diagnostic performance of CSF AD biomarkers.

Results: In 813 consecutive patients, median age 70 [interquartile range (IQR) = 63 - 77] including 132 patients over 80 years, we observed a similar confidence gain in CSF biomarkers between older and younger patients, both for AD and non-AD diagnoses. In older patients, the added value of CSF biomarkers was greater when CSF biomarkers indicated AD profile whereas the initial hypothesis was "non-AD", leading to a final diagnosis of AD (2.4 ± 1.6 versus 1.1 ± 2.1, p-value, p = 0.03). ROC analyses showed similar performance of AD CSF biomarkers in older and younger patients.

Conclusion: CSF AD biomarkers added substantial value to clinical assessment in patients over 80. Their use seems crucial in the diagnostic process for older adults referred to memory clinics.