The Preliminary indications
Purva rupa implies preliminary signs of disease. These symptoms appear before the actual onset of any illness, and are warning signs that disease may soon manifest. Each disease has specific preliminary signs. If there is any confusion about a specific diagnosis arising due to similar symptoms or causative factors, then the purva rupa needs to be considered. For example, in the case of epilepsy, the purva rupa includes dimness of vision, particular odors or tastes becoming prominent and a throbbing pain all over the body.

Source: http://www.jiva.com/ayurveda/about-ayurveda/110.html