Addressing @Patrick_Ryan post, the issue is PD is not diagnosed either early or late. Patients are diagnosed with various parkinsonisms nonspecifically for several visits b/c it is too subtle or the provider remains unsure of the diagnosis. Later, it is often clearly reasonably coded/diagnosed as PD (even though it is actually a neurodegenerative parkinsonism),. Then later visits are most accurately diagnosing the person with either PD (if it does not change for many years) or with a PSP/CBD/MSA parkinsonism. So the most accurate diagnosis is usually considered the most recent “set” of most consistent diagnoses (usually neurologists) b/c the primary care docs often just keep copying forward the erroneous PD diagnosis code even if the neurologist has diagnosed something differently later.
This is supported by the note that the <0.1% proportion have a secondary/neurodegenerative concept AFTER the last PD code.
We are intensely interested in the earliest entry/incidence date in our cohort, but to classify if the person is actually PD or Not PD requires look at the last several visits (and we suspect specialty, but that’s to be tested). The literature suggests that once you figure out someone has PD later, then the earliest “broad parkinsonism” concept counts as start of cohort which is how Atlas seems to work. I do lose this in the way @Gowtham_Rao and I constructed the unaminity algorithm.
I tried to copy/paste JSON in the post into Atlas-demo and I didn’t see a difference in the indexing of cohort start. See cohort 1781774:
