Image copyright RMIT University Image caption Computer software measures drawing speed and pen pressure to diagnose Parkinson's

A test that involves drawing a spiral on a sheet of paper could be used to diagnose early Parkinson's disease.

Australian researchers have trialled software that measures writing speed and pen pressure on the page.

Both are useful for detecting the disease, which causes shaking and muscle rigidity.

The Melbourne team said the test could be used by GPs to screen their patients after middle age and to monitor the effect of treatments.

The study, published in Frontiers of Neurology, involved 55 people - 27 had Parkinson's and 28 did not.

Speed of writing and pen pressure while sketching are lower among Parkinson's patients, particularly those with a severe form of the disease.

Image copyright RMIT University Image caption Treatment options are effective only when the disease is diagnosed early

In the trial, a tablet computer with special software took measurements during the drawing test and was able to distinguish those with the disease, and how severe it was.

Poonam Zham, study researcher from RMIT University, said: "Our aim was to develop an affordable and automated electronic system for early-stage diagnosis of Parkinson's disease, which could be easily used by a community doctor or nursing staff."

The system combines pen speed and pressure into one measurement, which can be used to tell how severe the disease is.

David Dexter, deputy research director at Parkinson's UK, said current tests for the disease were not able to accurately measure how advanced someone's condition was.

"This can impact on the ability to select the right people for clinical research, which is essential to develop new and better treatments for Parkinson's.

"This new test could provide a more accurate assessment by measuring a wider range of features that may be affected by Parkinson's, such as co-ordination, pressure, speed and cognitive function."

He added that the test could be a "stepping stone" to better clinical trials for Parkinson's.