ABSTRACT
Headache, like any other disease entity, requires a classification system. Diagnosis of the various headache disorders will be more accurate and universal when it has as its basis a consistent classification system and a set of scientifically derived diagnostic criteria. The ideal classification table should be sensitive, specific, exhaustive, generalizable, reliable and valid. Sensitivity occurs when patients with a particular form of headache are all diagnosed as such; specificity is when patients who do not have a particular disorder are invariably excluded. A classification table is exhaustive when its usage enables all headaches to be classified. It is generalizable when it can be used in diverse settings by both headache specialist and nonspecialist alike. Reliability occurs when the system has high inter-obsever repeatability with low variability. High correlation of diagnosis with the underlying biological disorder underlines validity.
