In 1987, the state of New York passed legislation instituting a DRG-based prospective payment system for all non-Medicare patients. The legislation included a requirement that the New York State Department of Health (NYDH) evaluate the applicability of the DRGs to a non-Medicare population. In particular, the legislation required that the DRGs be evaluated with respect to neonates and patients with Human Immunodeficiency Virus (HIV) infections. NYDH entered into an agreement with 3M HIS to assist with the evaluation of the need for DRG modifications as well as to make the necessary changes in the DRG definitions and software. The DRG definitions developed by NYDH and 3M HIS are referred to as the All Patient DRGs (AP DRGs).

The AP DRG code system is no longer updated as DRG classification system evolved to APR DRG. Evolution of DRG is summarized in the APR DRG methodology overview as well as in various articles.

Goldfield N. The evolution of diagnosis-related groups (DRGs): from its beginnings in case-mix and resource use theory, to its implementation for payment and now for its current utilization for quality within and outside the hospital. Qual Manage Health Care. 2010;19(1)3-16.

Averill RF, Goldfield NI, Muldoon J, Steinbeck BA, Grant TM. A closer look at All-Patient Refined DRGs. J AHIMA. 2002;73(1):46-49.

https://apps.3mhis.com/docs/Groupers/All_Patient_Refined_DRG/Methodology_overview_GRP041/grp041_aprdrg_meth_overview.pdf