Critical Access to Clinical Lab Services Act of 2004 - Amends title XVIII (Medicare) of the Social Security Act to provide that clinical diagnostic laboratory services furnished by a critical access hospital shall be treated as being furnished as part of outpatient critical access services without regard to whether: (1) the individual for whom the services are furnished is physically present in the critical access hospital at the time the specimen is collected; (2) such individual is registered as an outpatient on the records of, and receives such services directly from, the critical access hospital; or (3) payment is available for such services under the fee schedule established for clinical diagnostic laboratory tests.