17 Jun 2019

Early Alzheimer's Detection | ATR FTIR

Alzheimer’s disease is a chronic neurodegenerative disease that usually starts slowly and gradually gets worse over time. It is the cause of 60-70% of cases of dementia. Early symptoms include difficulty remembering recent events as well as problems with language, disorientation, mood swings, loss of motivation, not managing self-care and behavioural issues. As the person gets worse, they withdraw from family and society, bodily functions are lost, eventually leading to death. 1,2

The cause of Alzheimer’s disease is not well understood, it is believed that about 70% is inherited from parents, other factors which could possibly be a cause include a head injury, depression and hypertension. Mental and physical exercise and avoiding obesity may decrease the of risk of Alzheimer’s disease, however evidence supporting this is weak. In 2015, there were approximately 29.8 million people worldwide with Alzheimer’s disease. It most often begins in people over 65 years of age, although 4–5% of cases are early-onset Alzheimer's

In 2015, dementia resulted in about 1.9 million deaths.  3,4 15-20 years prior to the onset of symptoms it is believed that the folding behaviours of amyloid‐β (Aβ) peptides switches from the healthy α‐helical form to the pathological β‐sheet‐enriched secondary structures. These β‐sheet structures can aggregate forming seeds that eventually lead to a build-up of amyloid plaques. Whether these plaques are the cause, or a symptom of the Alzheimer’s disease is currently unknown. In either case detection of the build up of these plaques is essential for monitoring and treatment of Alzheimer’s, however current methods require invasive procedures to be performed.

Nabers et. alhave recently reported the potential for detection of biomarkers in the blood for this peptide change using a Specac ATR unit mounted in an FTIR spectrometer using the Amide I band position. The median band position for patients with Alzheimer’s was found to be several wavenumbers lower than the median band position compared to healthy patients and patients with other forms of dementia.

Cohort studies of blood samples taken from patients who were later diagnosed with Alzheimer’s were used to demonstrate that this technique could be used as a screening method to detect patients at risk of developing Alzheimer’s, with a mean collection time of 8 years prior to diagnosis.

By setting a threshold value of 1644 cm-1for the Amide I band 80% of patients who later went on develop Alzheimer’s would have been selected for more invasive follow up tests, although 30% of patients undergoing these procedures would not have the disease. Although this is a relatively high false negative rate with 20% of patients with Alzheimer’s wrongly being given the all clear this is still an advantage over the current system of waiting for the onset of symptoms before beginning invasive tests. 

The article that this paper is based on is titled ‘Amyloid blood biomarker detects Alzheimer's disease’ and the authors are Andreas Nabers Laura Perna, Julia Lange, Ute Mons, Jonas Schartner, Jörn Güldenhaupt, Kai - Uwe Saum, Shorena Janelidze, Bernd Holleczek, Dan Rujescu, ProfileOskar Hansson, ProfileKlaus Gerwert, Hermann Brenner. The article was published online at EMBO press. 

Reference 

1. Article - http://embomolmed.embopress.org/content/10/5/e8763#abstract-3
2. Commission de la transparence (June 2012). "Drugs for Alzheimer's disease: best avoided. No therapeutic advantage" [Drugs for Alzheimer's disease: best avoided. No therapeutic advantage]. Prescribe International21 (128): 150. PMID 22822592.
3. Burns A, Iliffe S (February 2009). "Alzheimer's disease". BMJ.
4."Dementia Fact sheet". World Health Organization. 12 December 2017.

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