From Major Diagnostic Category to All Patient Refined Diagnosis Related Groups
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After coding the primary diagnosis into ICD-9-CM, the ICD-9-CM are being grouped into Major Diagnostic Categories (MDC). Each MDC is assigned to an All Patient Refined Diagnosis Related Groups (APR-DRG), which is more homogeneous for medical treatment as for cost of treatment.
The Major Diagnostic Category is being used to calculate the average cost for each type of pathology and stay in the hospital to determine the acceptable activity (Dutch: verantwoorde activiteit). The acceptable activity is meant to match the activity within the hospital with its budget. In psychiatric hospitals or psychiatric departments of general hospitals, the equivalent Minimum Psychiatric Data (Dutch: Minimale Psychiatrische Gegevens: MPG; French: Registres de Données psychiatriques minimales: RPM) are being used.
The Major Diagnostic Categories are being converted into All Patient Refined Diagnosis Related Groups (APR-DRG), which are more homogeneous for medical treatment as for cost of treatment. The classification of cure data into DRGs was for the first time developed at Yale University in the USA in the early 1970s. The purpose of a classification into DRGs is to relate the case mix of pathology of the hospital to its resource demand. Patients are being grouped into groups of patients with similar clinical profiles and demand of hospital resources (Resource intensity as the relative volume and types of diagnostic, therapeutic, and bed services used in the management of a particular disease).
The original goal for the development of the Diagnosis Related Groups (DRG) was to develop a system in which patients could be classified related to the hospital resources they consumed. However due to the evolution of healthcare, a new classification was needed which allowed for more than clasifying based on resource usage, cost and payment. A system was needed which would allow for more monitoring and control of medical activities, which became the APR-DRG classification:
The APR-DRGs expand the basic DRG structure by adding four subclasses to each DRG. The addition of the four subclasses addresses patient differences relating to Severity of Illness (SOI) (degree of physiologic decompensation or organ system loss of function) and Risk of Mortality (ROM, refers to the likelihood of dying). SOI and ROM indicate the requirement for the relative volume and types of diagnostic, therapeutic and bed services used in the management of a particular disease. The four Severity of Illness subclasses and the four Risk of Mortality subclasses are numbered sequentially from 1 to 4 ranging from minor, moderate, major, up to extreme Severity of Illness or Risk of Mortality. To evaluate resource use or to establish patient care guidelines, the APR-DRG in conjunction with severity of illness (SOI) subclass is used. For the evaluation of patient mortality the APR-DRG in conjunction with the risk of mortality (ROM) subclass is being used. The APR-DRG should lead to a more appropriate indication of the utilization of resources for the hospital and physicians, based on a more accurate severity-adjusted Case Mix Index (CMI).
According to version 20 of APR-DRG there are 956 APR-DRG defined, which in turn are grouped into 26 Major Diagnostic Categories (MDC). The MDCs were created to ensure that the DRGs are clinically coherent. The diagnoses in each MDC corresponds to a single organ system or etiology and in general, MDCs are also associated with a particular medical specialty (medical, surgical). The basic organizing approach to classification in the APR-DRG system is to first assign the patient to a Major Diagnostic Category (MDC), based upon the principal diagnosis (PDX), and then to a specific APR-DRG category based upon principal diagnosis (if medical) or operating room procedure (if surgical). The principal diagnosis is the diagnosis at the end of care (final Dx). The secondary diagnosis (SDX) is about comorbity (existed before admission, POA: Present On Admission) or a complication (occurred after admission). The Principal Operation (POp) is the procedure or operation primarily done for the admission (PDX or SDX). A Secondary Operation (SOp) are all other significant procedures or operations.
Overview of the first categories of APR-DRG (Version 20) and their relation to the MDC:
| DRG-code | DRG description | MDC-code | MDC description | Medical (M) or Surgical (P) | ||
| 001 | Liver transplant | Pre-DC | liver transplant, heart- and/or lung transplant | P | ||
| 002 | Heart &/or lung transplant | Pre-DC | liver transplant, heart- and/or lung transplant | P | ||
| 003 | Bone marrow transplant | Pre-DC | liver transplant, heart- and/or lung transplant | P | ||
| 004 | Tracheostomy w long term mechanical ventilation w extensive procedure | Pre-DC | liver transplant, heart- and/or lung transplant | P | ||
| 005 | Tracheostomy w long term mechanical ventilation w/o extensive procedure | Pre-DC | liver transplant, heart- and/or lung transplant | P | ||
| 006 | Pancreas transplant | Pre-DC | liver transplant, heart- and/or lung transplant | P | ||
| 020 | Craniotomy for trauma | 01 | Nervous System | P | ||
| 021 | Craniotomy except for trauma | 01 | Nervous System | P | ||
| 022 | Ventricular shunt procedures | 01 | Nervous System | P | ||
| 023 | Spinal procedures | 01 | Nervous System | P | ||
| 024 | Extracranial vascular procedures | 01 | Nervous System | P | ||
| 025 | Nervous system proc for peripheral nerve disorders | 01 | Nervous System | P | ||
| 026 | Other nervous system &related procedures | 01 | Nervous System | P | ||
| 040 | Spinal disorders & injuries | 01 | Nervous System | M | ||
| 041 | Nervous system malignancy | 01 | Nervous System | M | ||
There are 25 Major Diagnostic Categories (MDC) defined:
In the APR-DRG system, the Severity of Illness (SOI) and Risk of Mortality (ROM) metrics are being used for mortality risk adjustment within each Diagnosis Related Groups (DRG). The SOI indicates how sick the patient is, while the ROM indicates the likelihood of death of the patient. Be aware that the SOI and ROM are categories and not scores. The four levels of SOI and ROM are:
Example of coding the SOI for Diabetes mellitus.
As an example, the ICD-9-CM code 001.0 stands for Cholera, due to Vibrio cholerae. This code belongs to Major Diagnostic Categories 06 (Diseases and Disorders of the Digestive System). This MDC is assigned to DRG 248 (Version 20, Major Gastrointestinal and Peritoneal Infections). The Severity of Illness is 1 (minor severity of illness) and the Risk of Mortality is 1 (minor risk of mortality). Based on these data the appropriate duration of the hospitalization for the patient can be calculated.
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First version published on 25 October 2010.
The author of this Webpage is Peter Van Osta.
Email: pvosta{at}gmail{dot}com