Major Diagnostic Categories (MDC)

The Major Diagnostic Categories (MDC) are formed by dividing all possible principal diagnoses (from ICD-9) into 25 mutually exclusive diagnosis areas. The diagnoses in each MDC correspond to a single organ system or etiology and in general are associated with a particular medical specialty. MDC 1 to MDC 23 are grouped according to principal diagnoses. Patients are assigned to MDC 24 (Multiple Significant Trauma) with at least two significant trauma diagnosis codes (either as principal or secondaries) from different body site categories. Patients assigned to MDC 25 (HIV Infections) must have a principal diagnosis of an HIV Infection or a principal diagnosis of a significant HIV related condition and a secondary diagnosis of an HIV Infection.

The IBIS system uses MDC in the Inpatient Hospital Discharge and the Emergency Department Encounter Query Modules.

Code List

(last updated September 2005)

This table uses 'DDs' as an abbreviation for "Diseases and Disorders."

MDC Definition
1 Nervous System
2 Eye
3 Ear, Nose, Mouth And Throat
4 Respiratory System
5 Circulatory System
6 Digestive System
7 Hepatobiliary System And Pancreas
8 Musculoskeletal System And Connective Tissue
9 Skin, Subcutaneous Tissue And Breast
10 Endocrine, Nutritional And Metabolic System
11 Kidney And Urinary Tract
12 Male Reproductive System
13 Female Reproductive System
14 Pregnancy, Childbirth And Puerperium
15 Newborn And Other Neonates (Perinatal Period)
16 Blood and Blood Forming Organs and Immunological Disorders
17 Myeloproliferative DDs (Poorly Differentiated Neoplasms)
18 Infectious and Parasitic DDs
19 Mental Diseases and Disorders
20 Alcohol/Drug Use or Induced Mental Disorders
21 Injuries, Poison And Toxic Effect of Drugs
22 Burns
23 Factors Influencing Health Status
24 Multiple Significant Trauma
25 Human Immunodeficiency Virus Infection

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