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Appendix. AHRQ Prevention Quality Indicators

The Prevention Quality Indicators (PQIs) are a set of measures that can be used with hospital inpatient discharge data to identify "ambulatory care sensitive conditions." These are conditions for which good outpatient care can potentially prevent the need for hospitalization or for which early intervention can prevent complications or more severe disease.41-42

Even though these indicators are based on hospital inpatient data, they provide insight into the quality of the health care system outside the hospital setting. For example, individuals with diabetes may be hospitalized for diabetic complications if their conditions are not adequately monitored or if they do not receive the patient education needed for appropriate self-management.

The PQIs consist of the 16 ambulatory care sensitive conditions listed.

For more information on the Prevention Quality Indicators, download the documentation and software at

For questions regarding the AHRQ Quality Indicators, E-mail the AHRQ Quality Indicator Support Team at

Prevention Quality Indicators

Chronic Conditions

  • Uncontrolled diabetes without complications.
  • Short-term diabetes complications.
  • Long-term diabetes complications.
  • Lower-extremity amputation among patients with diabetes.
Circulatory Diseases
  • Congestive heart failure.
  • Hypertension.
  • Angina without a procedure.
Respiratory Diseases
  • Adult asthma.
  • Pediatric asthma.
  • Chronic obstructive pulmonary disease.

Acute Conditions

  • Bacterial pneumonia.
  • Dehydration.
  • Urinary tract infection.
  • Perforated appendix.
  • Pediatric gastroenteritis.

Birth Outcomes

  • Low-weight birth.

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Source of Data for This Report

The results presented in this report are drawn from the HCUP, a Federal-State-Industry partnership to build a multi-State health care data system. This partnership is sponsored by AHRQ and is managed by staff in AHRQ's Center for Delivery, Organization, and Markets.

HCUP is based on data collected by individual State partner organizations (including State departments of health, hospital associations, and private agencies), which then provide the data to AHRQ. HCUP would not be possible without statewide data collection projects and their partnership with AHRQ.

For the year 2000, 29 State partner organizations contributed data to AHRQ, where all files were validated and converted into a uniform format. The uniform HCUP databases enable comparative studies of health care services and the use and cost of hospital care, including:

  • The effects of market forces on hospitals and the care they provide.
  • Variations in medical practice.
  • The effectiveness of medical technology and treatments.
  • Use of services by special populations.

HCUP includes short-term, non-Federal, community hospitals as defined by the American Hospital Association. This definition includes general hospitals and specialty facilities, such as pediatric, obstetrics-gynecology, and oncology hospitals. The HCUP State Inpatient Databases (SID) also include short-term rehabilitation facilities. Long-term care and psychiatric hospitals are excluded, as are substance abuse treatment facilities.

HCUP includes several sets of inpatient databases for health services research. This report is based on Nationwide Inpatient Sample (NIS) data for years 1994, 1997, and The NIS is the largest all-payer inpatient care database that is publicly available in the United States. The database contains data for 5 to 8 million hospital stays from roughly 1,000 hospitals sampled to approximate a 20 percent stratified sample of U.S. community hospitals.vii The data are weighted to obtain estimates representing the total number of inpatient hospital discharges in the U.S.; in the year 2000, this figure was approximately 36.4 million.

vi By 1994, 17 State Partners participated in HCUP (AZ, CA, CO, CT, FL, IL, IA, KS, MD, MA, NJ, NY, OR, PA, SC, WA and WI). By 1997, 5 additional State Partners (GA, HI, MO, TN and UT) participated. By 2000, 7 additional states (KT, ME, MI, NC, TX, VA, and WV) participated in HCUP. While Michigan participated in HCUP during 2000, Michigan data were not included in the 2000 NIS. Thus, analyses conducted for the Fact Book are based on 2000 NIS data sampled from 28 State Partner databases.
vii Starting in the year 2000, short-term rehabilitation hospitals are not included in the HCUP Nationwide Inpatient Sample (NIS).

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For this report, the AHRQ Prevention Quality Indicators are applied to the HCUP Nationwide Inpatient Sample hospital discharge databases.

The AHRQ Prevention Quality Indicators identify hospital admissions that could have been avoided, at least in part, through high quality outpatient care. These PQIs are based on existing measures that have been evaluated by health researchers and used in analytic studies.43

The AHRQ PQIs rely solely on hospital inpatient administrative data and, for this reason, serve as screens to examine quality and identify the need for more in-depth studies. The PQIs were originally developed by AHRQ staff and were recently revised and improved under contract with AHRQ by the University of California, San Francisco-Stanford University (UCSF-Stanford) Evidence-Based Practice Center.

Several steps are taken to apply the AHRQ Prevention Quality Indicators to HCUP hospital discharge data for this study:

  1. QI software was reviewed and modified to allow for the generation of national estimates using a weighted NIS.
  2. National, population-based data were acquired for the reporting categories in the study.
  3. HCUP data were prepared for consistency over time and data sets to account for longitudinal changes in ICD-9 codes.
  4. Statistical methods were developed for hypothesis testing.

The report, Methods Applying AHRQ Quality Indicators to Healthcare Cost and Utilization Project (HCUP) Data for the National Healthcare Quality Report,44 available from AHRQ upon request, describes these steps in detail.

The Prevention Quality Indicators develop admission rates using HCUP inpatient hospitalization data and population data from the 2000 Census and Claritas.45 Admission rates are based on principal diagnosis for all measures except diabetes-related lower extremity amputations, perforated appendix, and low-weight births. For these three PQIs, counts are included in the numerators if the condition of interest is indicated in any diagnosis field. The PQIs for perforated appendix and low-weight births use hospital discharges in the denominators, rather than general population groups. Diagnoses are identified using codes of the International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM). Risk adjustments are made for age and gender differences based on methods of direct standardization.46

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1 Source: Unpublished tables produced by AHRQ staff using the 2000 HCUP Nationwide Inpatient Sample. Costs are based on charges included in accounting data reported by hospitals to the Center for Medicare and Medicaid Services.

2 Centers for Disease Control and Prevention. 2002. National Diabetes Fact Sheet. Accessed December 10, 2003.

3 Mokdad A, Ford E, Bowman B, Dietz W. 2003. Prevalence of obesity, diabetes, and obesity-related health risk factors, 2001. Journal of the American Medical Association 289(1):76-9.

4 Diabetes Prevention Program Research Group. 2002. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. New England Journal of Medicine 346(6):393-403.

5 Centers for Disease Control and Prevention. U.S. Obesity Trends 1985 to 2002. Accessed March 19, 2009.

6 American Diabetes Association. Costs of Diabetes in U.S., 2002. Diabetes Care 26(3):917-33.

7 Institute of Medicine. 2003. Priority Areas for National Action: Transforming Health Care Quality. Washington, DC: National Academies Press.

8 U.S. Department of Health and Human Services. November 2000. Healthy People 2010: Understanding and Improving Health. 2nd ed. Washington, DC: U.S. Government Printing Office.

9 Institute of Medicine. 2003. Priority Areas for National Action: Transforming Health Care Quality. Washington, DC: National Academies Press.

10 American Heart Association. 2003. Heart Disease and Stroke Statistics—2004 Update. Dallas, TX: American Heart Association.

11 National Institutes of Health. High Blood Pressure.

12 American Heart Association. 2002. Heart Disease and Stroke Statistics—2003 Update. Dallas, TX: American Heart Association.

13 American Heart Association, 2003.

14 Ibid.

15 Ibid.

16 American Heart Association, 2002.

17 U.S. Department of Health and Human Services. 2000. Action Against Asthma: A Strategic Plan for the Department of Health and Human Services. Accessed March 19, 2009.

18 Krauss, N. March 2003. Statistical Brief #13: Asthma Treatment: Use of Medications and Devices, 2000. Rockville, MD: Agency for Healthcare Research and Quality. Accessed March 19, 2009.

19 Ibid.

20 American Lung Association. March 2003. Trends in Asthma Morbidity and Mortality.

21 U.S. Department of Health and Human Services, 2000.

22 U.S. Department of Health and Human Services. November 2000. Healthy People 2010: Understanding and Improving Health. 2nd ed. Washington, DC: U.S. Government Printing Office.

23 National Institutes of Health. 2003. Data Fact Sheet: Chronic Obstructive Pulmonary Disease. NIH Publication No. 03-5229. Bethesda, MD: National Institutes of Health.

24 American Lung Association. 2001. Breathless in America: COPD at a Glance.

25 National Institutes of Health, 2003.

26 Ibid.

27. Federson DS. 1993. Pneumococcal vaccination in the prevention of community-acquired pneumonia: An optimistic view of cost-effectiveness. Seminars in Respiratory Infection 8(4):285-93.

28 Foster DA, Taslma A, Furumoto-Dawson A, et al. 1992. Influenza vaccine effectiveness in preventing hospitalization for pneumonia in the elderly. American Journal of Epidemiology 136(3):296-307.

29 Weinberg AD, Minaker KL. 1995. Dehydration: Evaluation and management in older adults. Journal of the American Medical Association 274(19):1552-6.

30 Gupta K, Rubin R. 1999. Infections in the urinary tract. Scientific American Medicine, Volume 2, Part 7:1-9. New York, NY: Scientific American.

31 American Urological Association. Urinary Tract Infections in Adults. Accessed March 19, 2009.

32 Gupta K, Rubin R. 1999. Infections in the urinary tract. Scientific American Medicine, Volume 2, Part 7: 1-9. New York, NY: Scientific American.

33 Foxman B, Barlow R, D'Arcy H, et al. 2000. Urinary tract infection: Self-reported incidence and associated costs. Annals of Epidemiology 10(8):509-15.

34 Ibid.

35 Murkhart DM. 1999. Management of acute gastroenteritis in children. American Family Physician 60(9):2555-66.

36 Martin JA, Hamilton BE, Sutton PD, et al. 2003. Births: Final Data for 2002. National Vital Statistics Reports 52(10):17-8.

37 Shiono PH, Behrman RE. 1995. Low Birth Weight: Analysis and Recommendations. The Future of Children 5(1):4-18.

38 Alexander GR, Korenbrot CC. 1995. The Role of Prenatal Care in Preventing Low Birth Weight. The Future of Children 5(1):103-20.

39 Institute of Medicine. 2003. Priority Areas for National Action: Transforming Health Care Quality. Washington, DC: National Academies Press.

40 U.S. Department of Health and Human Services. November 2000. Healthy People 2010: Understanding and Improving Health. 2nd ed. Washington, DC: U.S. Government Printing Office.

41 Agency for Healthcare Research and Quality. 2001. AHRQ Quality Indicators—Guide to Prevention Quality Indicators: Hospital Admission for Ambulatory Care Sensitive Conditions. AHRQ Pub. No. 02-R0203. Rockville, MD: Agency for Healthcare Research and Quality.

42 Davies SM, Geppert J, McClellan M, et al. May 2001. Refinement of the HCUP Quality Indicators. Technical Review Number 4 (prepared by UCSF-Stanford Evidence-Based Practice Center under Contract No. 290-97-0013). AHRQ Pub. No. 01-0035. Rockville, MD: Agency for Healthcare Research and Quality.

43 Agency for Healthcare Research and Quality. 2001. AHRQ Quality Indicators—Guide to Prevention Quality Indicators: Hospital Admission for Ambulatory Care Sensitive Conditions. Rockville, MD: Agency for Healthcare Research and Quality. AHRQ Pub. No. 0-R0203.

44 Coffey R, Barrett M, Houchens B, et al. June 2003. Methods Applying AHRQ Quality Indicators to Healthcare Cost and Utilization Project (HCUP) Data for the National Healthcare Quality Report. Deliverable 179 (prepared by Medstat under Contract No. 290-00-004).

45 Claritas, Inc. May 2001. The Claritas Demographic Update Methodology.

46 Fleiss JL. 1973. Statistical Methods for Rates and Proportions. New York, NY: John Wiley & Sons, Inc.

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Angina (without a procedure)—Angina is a severe, often constricting pain, discomfort, tightness, or pressure experienced primarily in the chest. Pain may also be felt in the left shoulder, arms, neck, back, and throat. Angina is often an early sign of coronary artery disease. While not all angina admissions are preventable, it is possible that angina can be effectively managed on an outpatient basis if diagnostic procedures and/or surgical interventions are not required.

Asthma—This chronic lung disease is characterized by an inflammation of the lungs and may involve muscle spasms and airway constriction. Common symptoms of asthma include: coughing, wheezing, shortness of breath, and chest tightness. Asthma may be triggered by a host of environmental factors, including pollen, dust, smoke, exercise, illness, weather, and strong emotions.

Bacterial pneumonia—Infection of the lungs caused by bacteria that leads to irritation, swelling, and congestion of the lungs.

Chronic obstructive pulmonary disease (COPD)—Common name for the frequently coexisting conditions of chronic bronchitis and emphysema. Chronic bronchitis is an inflammation of the lungs that leads to swelling of the lungs and constriction of the airways. Emphysema is also an inflammation of the lungs leading to swelling that stretches and eventually breaks the walls in between the air sacs. These broken walls reduce the elasticity of the lungs and impair the exchange of oxygen and carbon dioxide.

Congestive heart failure (CHF)—A weakness in the heart muscle, possibly caused by heart attack, heart disease, high blood pressure, or infection that reduces the ability of the heart to effectively pump blood to the body. This inability to effectively pump and circulate blood throughout the body leads to pooling of blood in the extremities and congestion in the lungs.

Dehydration—Excessive loss of water and salt that can lead to dangerous side effects. Dehydration is usually classified as mild, moderate, and severe with symptoms. Mild and moderate dehydration are characterized by symptoms ranging from dry mouth and rapid heart beat to sunken eyes and lethargy. Severe dehydration can lead to shock, seizure, brain damage, and death.

Diabetes—The body's inability to produce insulin (type 1 diabetes) or properly use insulin (type 2 diabetes) that has been produced. Complications from diabetes can be categorized as follows:

  • Short-term complications—Conditions include diabetic ketoacidosis, hyperosmolarity, and coma. These life-threatening conditions occur when a patient experiences excess glucose or insulin.
  • Long-term complications—Conditions include renal, visual, neurological, and circulatory disorders.
  • Lower extremity amputation—Long-term circulatory problems caused by diabetes can lead to gangrene and necrosis of the muscle and skin in the legs; often, these complications will lead to the amputation of the feet and/or legs. Lower extremity amputations are often preventable with proper disease management. Hospitalizations involving these procedures signal significant problems in the quality of primary and preventive care that might have been provided earlier in the disease progression.

Hypertension—Also known as high blood pressure, hypertension is the elevation of blood pressure to a level sufficient to cause cardiovascular damage. The official criterion for hypertension is a systolic reading of 140 or higher and a diastolic reading of 90 or higher.

Low-weight birth—Birth weight less than 2,500 grams.

Pediatric gastroenteritis—Irritation and inflammation of the digestive tract in children. Common symptoms include abdominal pain, diarrhea, vomiting, nausea, and dehydration. A variety of environmental factors may be responsible, including food poisoning, viral infection, and intestinal parasites.

Perforated appendix—A tear in the appendix usually caused by swelling from appendicitis. This perforation allows the contents of the appendix to be released into the abdominal cavity and can lead to a serious infection (peritonitis).

Region—For this report, States are included in the four U.S. Census regions as follows:

  • Northeast—Connecticut, Massachusetts, Maine, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont.
  • Midwest—Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota, Wisconsin.
  • West—Alaska, Arizona, California, Colorado, Hawaii, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, Wyoming.
  • South—Alabama, Arkansas, Delaware, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, Virginia, West Virginia.

Urban/rural residence—This report defines patient residence as urban or rural based on the 1990 definition of the U.S. Office of Management and Budget. Thus, location of patient's residence is defined as:

  • Urban—Patient's ZIP Code is located in a metropolitan statistical area (MSA).
  • Rural—Patient's ZIP Code is located outside a MSA.

Urinary tract infection—Infection that occurs when bacteria enters the urethra. The infection may spread from the urethra to the rest of the urinary tract, including the bladder, ureters, and kidneys.

Note: Definitions are derived from 3 sources:

  1. AHRQ Quality Indicators — Guide to Prevention Quality Indicators: Hospital Admission for Ambulatory Care Sensitive Conditions. Rockville, MD: Agency for Healthcare Research and Quality, 2001. AHRQ Pub. No. 0-R0203
  2. Stedman's Medical Dictionary — 27th Edition. 2000. Baltimore, MD: Lippincott Williams & Wilkins.
  3. Agency for Healthcare Research and Quality. 2002. Description of Data Elements: Nationwide Inpatient Sample (NIS), Hospital Weights File, 2001. Accessed March 19, 2009.

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For More Information

More information regarding HCUP data is available at, as well as on the HCUP User Support Web site at Detailed documentation for the AHRQ Quality Indicators is available at

Additional descriptive statistics can be viewed through HCUPnet (, a Web-based tool providing easy access to information on hospital stays.

NIS Data Currently Available Include:

1999 (PB 2002-500020)
1998 (PB 2001-500092)
Release 6, 1997 (PB 2000-500006)
Release 5, 1996 (PB 99-500480)
Release 4, 1995 (PB 98-500440)
Release 3, 1994 (PB 97-500433)
Release 2, 1993 (PB 96-501325)
Release 1, 1988-1992 (PB 95-503710)

NIS data for the years 1988 to 2001 can be purchased for research through the HCUP Central Distributor sponsored by AHRQ: telephone: (866) 556-4287 (toll-free), fax: 866-792-5313, or e-mail:

Price of the data is $322 for Release 1; $160 per year for 1993 to 1999; and $200 per year for 2000 and 2001. All prices may be higher for customers outside the United States, Canada, and Mexico.

Previously published HCUP Fact Books are available online ( and from the AHRQ Publications Clearinghouse. To order by telephone, please call (800) 358-9295 with the title and publication number.

  1. Hospitalization in the United States, 1997 (HCUP Fact Book No. 1, AHRQ Publication No. 00-0031).
  2. Procedures in U.S. Hospitals, 1997 (HCUP Fact Book No. 2, AHRQ Publication No. 01-0016).
  3. Care of Women in U.S. Hospitals, 2000 (HCUP Fact Book No. 3, Publication No. 02-0044).
  4. Care of Children and Adolescents in U.S. Hospitals, 2003 (HCUP Fact Book No. 4, Publication No. 04-0004).

Impact Case Studies

AHRQ is always looking for ways in which AHRQ-funded research, products, and tools have changed peoples' lives, influenced clinical practice, improved policies, and affected patient outcomes. Impact case studies describe AHRQ research findings in action. These case studies have been used in testimony, budget documents, and speeches. If you are aware of any impact AHRQ-funded research or products, such as HCUP, have had on health care policy, clinical practice, or patient outcomes, please let us know using the contact information below.

Healthcare Cost and Utilization Project (HCUP)
Agency for Healthcare Research and Quality
Phone: 866-290-HCUP

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AHRQ Publication No. 04-0056
Current as of September 2004


The information on this page is archived and provided for reference purposes only.


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