Origin of DRGs

The first functional set of DRGs was developed in the early 1970s. 

The process of forming the original DRGs was begun by dividing all possible principal diagnoses into multiple mutually exclusive PDX categories referred to as Major Diagnostic Categories (MDCs). 

The MDCs were formed by expert panels as the first step toward ensuring that the DRGs would be clinically coherent. The diagnoses in each MDC correspond to a single Organ System

or etiology and in general, are associated with a particular medical specialty. Thus, in order to maintain the requirement of clinical coherence, no final DRG could contain patients in different MDCs.