Prevalence studies, if conducted correctly, should iron out any
inconsistencies due to any historical misdiagnosis, methodology
is not based on a " head count " as such but focuses on
diagnosing prevalence based on a known discreet population.
however, the evidence avaiable in respect of CH sufferers
is still scant and often contradictory.

prevalence has been assessed in six major studies to date
if you exclude potentially dodgy chinese survey. of these,
prevalence ranges from just 56% per 100,000 ( 0.06% )
to 401 per 100,000 ( 0.40% ). If you average out all six
studies ( which is pretty legitimate ) it is 138 per 100,000(0.14%).

Still many people remain un/misdiagnosed despite the increase
in awareness of the disease.