Do we yet have any good avoidance or mitigation regimes, be they drug or otherwise for people who show positive on a test like this? The alternative is that it lets you put things in place for when you lose agency.

Good as in scientifically proven. Not speculative fantasy.

This Alzheimer's blood test, PrecivityAD2, is based on the p-tau217 biomarker.

In one recent study, people very high p-tau217 had a 38% chance of progressing to cognitive impairment within 5 years vs 12% for those with low levels. The current tests cost about $200-300, so they're not unreasonable as a screening test.