<prompt> The Starch iodine test is useful to diagnose:Wegeners granulomatosisCat scratch diseaseSarcoidosisFreys syndrome  <response>: The Starch iodine test is useful to diagnose Freys syndrome. This involves painting the affected area with iodine, which is allowed to dry before applying dry starch, which turns blue on exposure to iodine in the presence of sweat. Sweating is stimulated by salivary stimulation. 