Much of the established biomarker development for AD has been performed using cerebrospinal fluid (CSF) as the specimen source. Because of the direct contact between CSF and the brain, the use of CSF as the sample source has been very critical for the development of AD biomarker assays. Moreover, brain-specific proteins or biomarkers are typically present at much higher concentration in CSF than in other body fluids such as blood or urine. Biomarkers are typically present at relatively low concentrations in the blood because the blood-brain barrier prevents the free passage of molecules between the CNS and blood compartments.
However, there are certain limitations to the use of CSF. One of the main limitations for using CSF is the invasiveness of performing a spinal tap to obtain the CSF sample. In addition, the high cost associated with the CSF collection and subsequent testing is somewhat limiting. In recent years, several blood-based assays that measure biomarkers for AD have been developed. Using blood, these assays eliminate the invasive use of a spinal tap and also provide for a more cost-effective and less time-consuming approach to testing.
On-going efforts continue to develop comparable biomarker tests using blood. Since brain-specific biomarkers are at much lower concentrations in the blood than in CSF, blood-based biomarker assays for AD use ultrasensitive measurement techniques to identify and quantify specific biomarkers. Blood-based tests are currently available for the measurement of several AD biomarkers including tau proteins and AB peptides.
Rather than using CSF biomarkers, dementia researchers currently tend to use blood-based biomarkers because of the ease of collection (less invasive), more cost-effective and less time consuming. Typically, blood-based biomarker assays for AD are not currently used in physician offices and other clinical settings.
In conclusion, blood-based biomarker tests for AD assessment are available, but CSF-based biomarker tests are currently more readily available. At present, blood-based tests tend to be used mainly by dementia researchers rather than by physicians in clinical settings.
