Abbreviation for Clinical Laboratory Improvement Amendments. Federal legislation and the personnel and procedures established by it under the aegis of the Health Care Financing Administration (HCFA) for the surveillance and regulation of all clinical laboratory procedures in the United States.The Clinical Laboratory Improvement Amendments of 1988 (CLIA 88) were passed by Congress in response to public concerns about the quality of laboratory testing, particularly in physician's office laboratories and in Papanicoloau smear interpretation. This legislation brought all 150,000 U.S. clinical laboratories, including physician's office laboratories, under uniform regulations. A clinical laboratory is defined as any facility where materials derived from the human body are examined for the purpose of providing information for the diagnosis, prevention, or treatment of disease or the assessment of health. Standards applied to laboratory personnel and procedures are based on test complexity and potential harm to the patient. The regulations establish application procedures and fees for CLIA registration, enforcement and surveillance methods, and sanctions applicable when laboratories fail to meet standards. CLIA regulations define three categories of testing complexity: waived, moderate, and high. For tests of moderate or high complexity, the laboratory must participate in a continuing program of proficiency testing whereby an independent laboratory periodically submits specimens of known composition for testing.