We can all agree with the need for better biomarkers. But what do we do in the meantime?

Consider the difficulties of trying to assess the efficacy of a drug which has true figures, but unknown to us (that's what we're trying to find out):
- for half of PwP, reduces progression on average by 10% (that is a progression rate of 10% per year would be reduced to 9% per year)
- for half of PwP has on average no effect.

The testing of drugs to slow or even reverse the progression of PD is harder than those for symptomatic control. There are smaller day to day changes, leading to longer test periods being required to see a meaningful difference. The longer time required for testing leads to the ethical issue of how can we demand patient compliance, possibly for years, without any obvious benefit to themselves.

There are two types of danger. One, where the use of a poor metric leads to a drug with no benefit being approved. The other, where the use of a poor metric results in the opposite effect: some truly efficacious therapies being wrongly labelled as failures.

There is the issue of the cost of the test. Tests that require patients to travel to a test centre, and tests that need to be administered by medics are costly, leading to fewer data points. The balance needs to be struck between cheap/less valid tests, probably internet based, and expensive/more valid tests. Also, the high cost of testing will lead to some drugs never being developed and, for those that do come to market, being exceedingly expensive.

John