Is there an epidimiological way to define rare and common diseases ?

  • $\begingroup$ How about doing it by the case numbers? $\endgroup$ – Chris Jul 21 '15 at 12:57
  • $\begingroup$ Could you please explain me better your suggestion ? I'm not sure to understand it correctly. $\endgroup$ – MauroM Jul 21 '15 at 13:42
  • $\begingroup$ A rare disease has very low case numbers, while common diseases occur in much higher numbers. $\endgroup$ – Chris Jul 21 '15 at 14:03
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    $\begingroup$ Thanks for the clarification ! Do you know if there is a threshold between the two cases ? $\endgroup$ – MauroM Jul 21 '15 at 14:11
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    $\begingroup$ To those who voted to close: This question is great, multiple countries build their Health systems budget according to their definitions of "rare" disease. In addition, the issue of these definitions is of great importance for the community health as well. $\endgroup$ – Ilan Jul 22 '15 at 7:41

While "common disease" has obscure incidence and prevalence definitions, "Rare" or "orphan disease" is more defined.

In the US, the rare disease defined as a condition which affect one (or less) of 200,000 people in population. However, this definition can be different in other countries, p.e. in Japan 1:50,000 or less.

We can assume that "common" disease is much frequent than "rare" one, thus the incidence and prevalence are much greater than per "rare disease" definition. However, again, there is no agreement of clear cut of "common disease" incidence and prevalence.

  • $\begingroup$ Thanks for the answer !! I think to have read something similar years ago, but not in detail... i would vote your answer but i still have a low reputation so i can't. $\endgroup$ – MauroM Jul 22 '15 at 9:58

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