New tests involving blood and brain scans can detect symptoms of Alzheimer's, and brief appraisals of real-life functioning can predict who is likely to develop it, researchers have said.

No drugs can significantly affect Alzheimer's disease though four have a very modest impact if given early on. The disease is very difficult to detect until it has progressed from mild memory loss to clear impairment. Detecting the disease early can help patients and their families plan better for the future but can also help researchers develop drugs to treat and perhaps even prevent the disease.

Anders Lonneborg and colleagues of DiaGenic, a biotech company based in Oslo, found a set of 96 genes that look different in the blood of Alzheimer's patients when compared to the same genes in healthy people. Their study of more than 100 older people, half from memory clinics and half from senior centres, found Alzheimer's accurately 85% of the time.

They identified genes related to the immune system, to inflammation and to cell division. The company has applied to regulators in the US and Europe to approve the test, Lonneborg told a meeting of the Alzheimer's Association in Washington.

Christos Davatzikos and colleagues at the University of Pennsylvania used a combination of PET and MRI scans to diagnose Alzheimer's. Positron emission tomography or PET scans can be used to measure blood flow in the brain in real time, while magnetic resonance imaging or MRI can clearly show the shape and size of physical structures in the brain.

This method found all 15 cases of mild cognitive impairment - a first step towards Alzheimer's - and cleared 15 healthy volunteers.

"This abnormal pattern of brain structure and blood flow detected not only mild cognitive impairment but even earlier ... when they were clinically normal," Davatzikos said.

Deborah Barnes and colleagues at the University of California San Francisco used simpler measures. They included measures like taking down scores on a simplified version of a standard cognitive exam.