Professor of cognitive neurology here

There is research into using gaze behavior (eye movements during targeted cognitive assessments) to develop an objective test of attention symptoms, but otherwise no. The screeners (questionnaires) are all very subjective, and a true diagnosis requires an extensive interview which is also subjective as it requires accurate recognition of one's past behavior. Which is difficult, because the things you don't pay attention to often don't get remembered.

My main focus is on using gaze and speech behavior to diagnose Alzheimers disease and other dementias, but I am planning to expand my research to ADHD in the next few years.

I also have ADHD, and I'm motivated because my kids will probably have it as well.