 Except in medical emergency situations, patients need a referral from the PCP in order to see a specialist or other doctor, and the gatekeeper cannot authorize that referral unless the HMO guidelines deem it necessary.Some HMOs pay gatekeeper PCPs set fees for each defined medical procedure they provide to insured patients (fee-for-service) and then capitate specialists (that is, pay a set fee for each insured person's care, irrespective of which medical procedures the specialists performs to achieve that care), while others use the reverse arrangement.Open-access and point-of-service (POS) products are a combination of an HMO and traditional indemnity plan.