If PH is suspected but there is uncertainty about the diagnosis, the patient should be referred to an allergy specialist, if possible, for epicutaneous & intradermal skin testing (progesterone challenge). The positive and negative predictive values of progesterone skin testing are unknown. Therefore, a negative skin test result does not exclude the diagnosis, and there can be an irritant false-positive response. 

Gonadotropin-releasing hormone (GnRH) agonists, such as Leuprolide, may be used for a challenge test.