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Healthcare Cost and Utilization Project (HCUP). HCUP Facts and Figures, 2006: Statistics on Hospital-Based Care in the United States [Internet]. Rockville (MD): Agency for Healthcare Research and Quality (US); 2008.

Cover of HCUP Facts and Figures, 2006: Statistics on Hospital-Based Care in the United States

HCUP Facts and Figures, 2006: Statistics on Hospital-Based Care in the United States [Internet].

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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 following four systems are used within this report to identify specific diagnoses and procedures: International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM), Clinical Classifications Software (CCS), Diagnosis Related Groups (DRGs), and Major Diagnostic Categories (MDCs).

The most detailed system is the ICD-9-CM that contains over 13,600 detailed diagnoses and 3,700 detailed procedures. 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.

To make the number of ICD-9-CM diagnoses and procedures more manageable, AHRQ has designed the CCS tool that groups ICD-9-CM codes into about 280 diagnostic and 230 procedure categories. This software aggregates similar diagnoses or procedures into clinically meaningful categories. More information on CCS can be found online ( 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.

In addition, diagnoses can also be grouped into DRGs. DRGs comprise a classification system that categorizes patients into groups, which are clinically coherent and homogeneous with respect to resource use. DRGs group patients according to diagnosis, type of treatment (procedures), age, and other relevant criteria. Each hospital stay has one DRG assigned to it. The Centers for Medicare and Medicaid Services (CMS) uses this classification system as a basis for Medicare payments for inpatient hospital stays.

DRGs, in turn, can be summarized into MDCs, which are broad groups of DRGs such as Diseases and Disorders of the Nervous System or Diseases and Disorders of the Eye. Each hospital stay has one DRG and one MDC assigned to it.

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.



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

176Contraceptive and procreative management (birth control or helping with conception)
177Spontaneous abortion
178Induced abortion
179Postabortion complications (complications following abortion)
180Ectopic pregnancy (abdominal or tubal pregnancy)
181Other complications of pregnancy
182Hemorrhage during pregnancy, abruptio placenta, placenta previa (bleeding and placenta disorders during pregnancy)
186Diabetes or abnormal glucose tolerance complicating pregnancy, childbirth, or the puerperium (diabetes or high blood glucose during pregnancy)
187Malposition, malpresentation (breech birth and other disorders of baby’s position during birth)
188Obstructed labor or fetopelvic disproportion
194Forceps delivery
195Other maternal complications of birth, puerperium affecting management of mother (other maternal complications of birth and period after childbirth)



Two steps were used to define maternal and infant procedures. First, all maternal and newborn stays were identified using the following codes:

Maternal stays were identified using Major Diagnostic Code 14: Pregnancy, childbirth and the puerperium.

Newborn stays were identified using the following CCS codes:

219Short gestation, low birth weight, and fetal growth retardation
220Intrauterine hypoxia and birth asphyxia (lack of oxygen to baby in uterus or during birth)
221Respiratory distress syndrome
222Hemolytic jaundice and perinatal jaundice
223Birth trauma
224Other perinatal conditions (other conditions occurring around the time of birth)

Second, maternal and newborn stays were examined for the following CCS all-listed procedures that were typically associated with maternal and infant stays:

Maternal procedures:

133Episiotomy (surgical incision into the perineum and vagina to prevent traumatic tearing during delivery)
134Cesarean section
135Forceps, vacuum, and breech delivery
136Artificial rupture of membranes to assist delivery
137Other procedures to assist delivery
138Diagnostic amniocentesis (diagnostic sampling of the fluid in the amniotic sac)
139Fetal monitoring
140Repair of obstetric laceration
141Other therapeutic obstetrical procedures

Infant procedures:

220Ophthalmologic and otologic diagnosis and treatment (vision and hearing diagnosis and treatment)
228Prophylactic vaccinations and inoculations



Top 6 most expensive circulatory system diagnoses:

100Acute myocardial infarction (heart attack)
101Coronary atherosclerosis (coronary artery disease)
102Non-specific chest pain
106Cardiac dysrhythmias (irregular heart beat)
108Congestive heart failure
109Acute cerebrovascular disease (stroke)



Childbirth DRG categories:

370Cesarean section with complications and comorbidities
371Cesarean section without complications and comorbidities
372Vaginal delivery with complicating diagnoses
373Vaginal delivery without complicating diagnoses
374Vaginal delivery with sterilization and/or dilation and curettage
375Vaginal delivery with operating room procedure except sterilization and/or dilation and curettage

Within DRG 370–371 and 372–375, all-listed diagnoses were also subsetted using the following CCS diagnosis categories to produce repeat C-section and Vaginal Birth After C-section (VBAC):

189Previous C-section

Childbirth complication CCS categories:

59Deficiency and other anemia
182Hemorrhage during pregnancy, abruptio placenta, placenta previa (bleeding and placenta disorders during pregnancy)
183Hypertension complicating pregnancy, childbirth, and the puerperium (high blood pressure during pregnancy)
184Early or threatened labor
186Diabetes or abnormal glucose tolerance complicating pregnancy, childbirth, or the puerperium (diabetes or high blood glucose during pregnancy)
187Malposition, malpresentation (breech birth and other disorders of baby’s position during birth)
188Obstructed labor or fetopelvic disproportion
189Previous C-section
191Polyhydramnios and other problems of amniotic cavity (excess amniotic fluid and other problems of amniotic cavity)
192Umbilical cord complication

Infant delivery type ICD-9-CM codes:

V30–V39Liveborn infants
.00delivered without mention of cesarean delivery (vaginal delivery)
.01delivered by cesarean delivery

Infant complication ICD-9-CM codes (selected ICD-9-CM codes were grouped together for graphic display):

Preterm birth:

765.0Extreme immaturity
765.1Other preterm infant

Meconium aspiration:

770.1Fetal and newborn aspiration

Post-birth respiratory problems:

770.8Other respiratory problems after birth

Neonatal jaundice:

774.2Neonatal jaundice associated with preterm delivery
774.6Unspecified fetal and neonatal jaundice

Other conditions listed separately:

761.1Premature rupture of membrane affecting newborn
766.0Exceptionally large baby
766.1Heavy-for-dates infant
768.3Fetal distress during labor
769Respiratory distress syndrome
770.6Transitory tachypnea
772.6Cutaneous hemorrhage
773.1Hemolytic disease due to ABO isoimmunization
775.0“Infant of a diabetic mother” syndrome
775.6Neonatal hypoglycemia
779.3Feeding problems


Depression ICD-9-CM codes:

293.83Mood disorder in conditions classified elsewhere- Transient organic psychotic condition, depressive type
296.2Major depressive disorder, single episode
296.3Major depressive disorder, recurrent episode
300.4Dysthymic disorder
311Depressive disorder, not elsewhere classified

Other Mental Health and Substance Abuse Secondary Conditions were identified in the following CCS-MHSA categories that were created using the CCS-MHSA tool:

650Adjustment disorders
651Anxiety disorders
652Attention-deficit, conduct, and disruptive behavior disorders
653Delirium, dementia, and amnestic and other cognitive disorders
654Developmental disorders
655Disorders usually diagnosed in infancy, childhood, or adolescence
656Impulse control disorders, not elsewhere classified
657Mood disorders
658Personality disorders
659Schizophrenia and other psychotic disorders
660Alcohol-related disorders
661Substance-related disorders


Cancer CCS categories:

11Cancer of head and neck
12Cancer of esophagus
13Cancer of stomach
14Cancer of the colon
15Cancer of rectum and anus
16Cancer of liver and intrahepatic bile duct
17Cancer of pancreas
18Cancer of GI organs and peritoneum
19Cancer of bronchus, lung
20Cancer, other respiratory and intrathoracic
21Cancer of bone and connective tissue
22Melanomas of skin
23Other non-epithelial cancer of skin
24Cancer of breast
25Cancer of uterus
26Cancer of cervix
27Cancer of ovary
28Cancer of other female genital organs
29Cancer of prostate
30Cancer of testis
31Cancer of other male genital organs
32Cancer of bladder
33Cancer of kidney and renal pelvis
34Cancer of other urinary organs
35Cancer of brain and nervous system
36Cancer of thyroid
37Hodgkin’s disease
38Non-Hodgkin’s lymphoma
40Multiple myeloma
41Cancer, other primary
43Malignant neoplasm without specification of site
44Neoplasms of unspecified nature or uncertain behavior
**Multiple cancer sites
**No specific sites listed

CCS Diagnosis Code 42 ‘Secondary malignancies’ and 45 ‘Maintenance chemotherapy, radiotherapy’ were reclassified and discharges were assigned to a specific cancer category listed as a secondary condition. If no secondary cancer diagnosis was listed, then discharges for CCS diagnosis codes 42 and 45 were counted as ‘No specific sites listed.’ If multiple secondary CCS diagnoses were listed, then CCS diagnosis codes 42 and 45 discharges were counted as ‘Multiple cancer sites.’


Asthma CCS category:


Arthritis CCS categories:

202Rheumatoid arthritis and related disease


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