Referral Network

Key facts

Federal self-referral law

Physician Self-Referral Law (Stark Law), Social Security Act Section 1877

Stark Law regulations

42 CFR Part 411, Subpart J

Federal kickback law

Anti-Kickback Statute, 42 U.S.C. 1320a-7b(b)

Common data signals

Referring or ordering provider NPIs on claims, and shared patients

What is a referral network?

A referral network describes who sends patients to whom. A primary care physician refers a patient to a cardiologist, the cardiologist orders imaging at a hospital, and the hospital discharges the patient to a skilled nursing facility. Each handoff is a link, and the links across a market form the network.

Networks are usually analyzed as graphs. Providers and facilities are nodes, and the links between them are weighted by the number of patients or claims they share. Influential nodes, such as a primary care group that feeds several specialists, stand out once the graph is built.

How referral networks are measured

No public dataset records every referral directly, so analysts infer networks from several signals:

• Referring and ordering provider fields: professional claims carry a referring or ordering National Provider Identifier (NPI) for services such as imaging, laboratory tests and durable medical equipment.
• Shared patients: two providers who treat the same patients within a short window are likely connected. CMS has published physician shared patient patterns data derived from Medicare claims for some past years.
• Organizational ties: common practice locations, group billing, hospital affiliations and accountable care organization membership.
• Sequence of care: a primary care visit followed by a specialist visit for the same diagnosis suggests a referral even without a referring provider field.

Why referral networks matter

Medical device and pharmaceutical commercial teams use referral networks to find the physicians who influence where patients go, not only those who treat the most patients. Health system strategy teams use them to see which physicians send patients to competitors, which is the basis of patient leakage analysis.

Payer network teams use referral patterns to design narrow networks that keep existing care relationships intact, and accountable care organizations use them to see where attributed patients receive care outside the organization.

Referral networks and federal law

Referral relationships are regulated. The Anti-Kickback Statute makes it a crime to knowingly offer or pay anything of value to induce referrals of items or services paid by federal health care programs. The Physician Self-Referral Law, known as the Stark Law, bars physicians from referring Medicare patients for designated health services to entities with which they or an immediate family member have a financial relationship, unless an exception applies.

Mapping a referral network is ordinary analysis. Legal risk begins when compensation, gifts or other incentives are tied to the volume or value of referrals.