Unit of Analysis

The unit of analysis is the hospital stay rather than the patient. All discharges have been weighted to produce national estimates.

Coding Diagnoses and Procedures

Diagnoses and procedures associated with an inpatient hospitalization can be defined using several different medical condition classification systems. The Clinical Classifications Software (CCS) was used predominantly within this report to identify specific diagnoses and procedures. CCS is based on the International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM), a uniform and standardized coding system containing over 13,600 diagnosis codes and 3,700 procedure codes. Each discharge record in the NIS is associated with one or more ICD-9-CM diagnosis code(s) and may contain one or more ICD-9-CM procedure code(s) if a procedure was performed during that hospitalization. Each hospital stay can have multiple CCS diagnoses and multiple CCS procedures.

In the CCS, ICD-9-CM codes are clustered into a smaller number of clinically meaningful categories that are sometimes more useful for presenting descriptive statistics than are individual ICD-9-CM codes. CCS codes are used extensively in this report to define groups of diagnoses and procedures for analysis. The CCS codes allow the reader to quickly and easily recognize patterns and trends in broad categories of hospital utilization. More information on CCS can be found online (http://www.hcup-us.ahrq.gov/toolssoftware/ccs/ccs.jsp). Specific CCS conditions or diagnoses can also be summarized into CCS body system or condition categories, which are broad groups of CCS conditions, such as Neoplasms, Mental Disorders, and Diseases of the Circulatory System.

Exhibit Diagnoses and Procedures

Throughout this report, combinations of diagnostic and procedure codes are used to isolate specific conditions or procedures. These codes are defined below by exhibit number.

SECTION 1 — OVERVIEW STATISTICS FOR INPATIENT HOSPITAL STAYS

EXHIBIT 1.3

Reasons for hospital stays are based on principal diagnosis defined by the following Major Diagnostic Categories (MDC):

SECTION 2 — INPATIENT HOSPITAL STAYS BY DIAGNOSIS

EXHIBIT 2.1

Discharges for pregnancy, childbirth and newborn infants were identified as those assigned to Major Diagnostic Category 14 (Pregnancy, childbirth and the puerperium) or as having one of the following CCS diagnosis codes, which constitute total infant discharges:

Maternal CCS categories not listed on the exhibit table but included in total maternal discharges:

SECTION 3 — INPATIENT HOSPITAL STAYS BY PROCEDURE

EXHIBIT 3.1 (graphic)

Childbirth-related hospitalizations were defined using the following Diagnosis Related Groups (DRG) for 1997:

Childbirth-related hospitalizations:

Childbirth-related hospitalizations were defined using the following Diagnosis Related Groups (DRG) for 2008:

Childbirth-related hospitalizations:

SECTION 4 — SPENDING FOR INPATIENT HOSPITAL STAYS

EXHIBIT 4.5

See definition for Major Diagnostic Categories (MDC) under Exhibit 1.3 above.

Maternal/neonatal is the sum of MDC 14 (Pregnancy, childbirth and the puerperium) and MDC 15 (Newborns and other neonates with conditions originating in the perinatal period).

SECTION 5 — HOSPITAL CARE FOR MENTAL HEALTH AND SUBSTANCE ABUSE CONDITIONS

EXHIBIT 5.1

MHSA stays were defined by CCS diagnostic codes for principal MH and SA stays.

MH-related disorders:

SA-related disorders:

EXHIBIT 5.2

Depression and bipolar disorders were defined by the following ICD-9-CM principal diagnosis codes.

Depression:

Bipolar disorders:

EXHIBIT 5.7, 5.10, 5.11

Pregnancy -related MH disorders were defined by the following ICD-9-CM principal diagnosis code:

EXHIBIT 5.11

Alcohol-related and drug-related disorders were defined by the following ICD-9-CM principal diagnosis codes:

EXHIBIT 5.12

In addition to the MHSA diagnoses listed in Exhibit 5.1, emergency department MHSA visits included:

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