Chapter 1. Introduction and Methods

National Healthcare Quality Report, 2008


In 1999, Congress directed the Agency for Healthcare Research and Quality (AHRQ) to produce an annual report, starting in 2003, on health care quality in the United States (42 U.S.C. 299b-2(b)(2)). AHRQ, with support from Department of Health and Human Services and private sector partners, designed and produced the National Healthcare Quality Report (NHQR) to respond to this legislative mandate.

This is the sixth annual report on the state of health care quality nationally. Similar to the previous five reports, it is designed to summarize data across a wide range of patient needs, including staying healthy, getting better, living with chronic illness and disability, and coping with the end of life. The report tracks quality across nine condition areas and tells the reader how effective, safe, timely, patient-centered, and efficient care is in the United States today.

The National Healthcare Quality Report presents data at the national and State levels, where State-level data are available. This sixth report seeks to balance the goal of presenting a consistent overview of the annual state of health care quality in the United States with the need to reflect changes in particular health care measures. In addition, the report incorporates methodological improvements in quantifying trends in health care quality.

The first NHQR, released in 2003, was a comprehensive national overview of the quality of health care the general U.S. population received. The 2004 NHQR initiated a second critical goal of the report series: tracking the Nation's quality improvement progress. The 2005 NHQR introduced a set of core measures and a variety of new composite measures. The 2006 NHQR continued to improve data, measures, and methods, adding new databases and measures and refining methods for quantifying and tracking changes in health care. The 2007 report, in addition to including new measures and data sources, presented an informed look at directions in health care quality based on data presented in the first five reports.

This 2008 NHQR continues to focus on a consistent subset of measures (the "core" measures), which includes the most important and scientifically supported measures in the full NHQR measure set. In addition, other measures (either new to the measure set or included in past years as part of the Data Tables appendix) are included to complement core measures in key areas. For example, five additional patient safety measures are discussed for the first time in the report (Chapter 3). These additional measures reflect increased awareness of the importance of health care quality as it relates to patient safety, following the passage of the Patient Safety and Quality Improvement Act of 2005.

Finally, to provide context for discussion and evaluation of the measures and data presented in the report, references have been systematically updated. Annual reports and other regularly released publications have been updated as appropriate. In addition, a wide range of peer-reviewed journals and electronically published articles have been searched for inclusion as references.

This chapter summarizes the methodological approaches AHRQ has taken in producing the 2008 NHQR. This year's report includes fewer changes to the measure sets and data sources than the past few years. Therefore, unlike past years, this chapter does not include separate sections listing changes to the measure set or new data sources. Changes in measures, data sources, and other modifications are summarized below. Material that is new in this year's report includes:

  • A new core measure for daily preventive asthma medication use.
  • New noncore measures for:
    • State variation in influenza immunization.
    • Receipt of minimally adequate treatment by adults with mental disorders.
    • Patient safety:
      • Surgical discharges with catheter-associated urinary tract infection.
      • Accidental puncture or laceration.
      • Postoperative wound separation.
      • Iatrogenic pneumothorax.
      • Deaths in low-mortality diagnosis-related groups.
    • Referral to hospice at the right time.
  • A discussion in Chapter 6, Efficiency, of a new approach to examining potentially avoidable rehospitalizations.

The new mental health measure for receipt of minimally adequate treatment by adults with mental disorders uses data from a new data so Substance Abuse and in more detail in the Measures Specifications appendix. By including the specification for "minimally adequate treatment," this measure improves on the measure in previous reports, which did not include criteria for the type or frequency of treatment.

As in previous years, the 2008 NHQR was written by AHRQ staff, with the support and guidance of AHRQ's National Advisory Council and the Interagency Work Group for the NHQR.

 

How This Report Is Organized

The basic structure of the report consists of the following:

  • Highlights summarizes key themes and highlights from the 2008 report.
  • Chapter 1: Introduction and Methods documents the organization, data sources, and methods used in the 2008 report and describes major changes from previous reports.
  • Chapter 2: Effectiveness examines the quality of health care in the general U.S. population, focusing on nine clinical conditions or care settings based largely on Healthy People 2010 condition areas. Measures of the quality of health care used in this chapter are identical to measures used in the National Healthcare Disparities Report (NHDR) except when data to examine disparities are unavailable for inclusion in the NHDR.
  • Chapter 3: Patient Safety tracks measures of patient safety, including postoperative complications, other complications of hospital care, and complications of medications.
  • Chapter 4: Timeliness examines the delivery of time-sensitive clinical care and patient perceptions of the timeliness and accessibility of their care.
  • Chapter 5: Patient Centeredness tracks patients' experiences with care in an office or clinic and satisfaction with communication during a hospital stay in order to incorporate the patient's experience and perspective into the report.
  • Chapter 6: Efficiency presents a conceptual view and exploratory analyses of this dimension of health care performance that has been missing from previous releases of the NHQR.

Appendixes are available online and include the following:

  • Appendix A: Data Sources provides information about each database analyzed for the NHQR, including data type, sample design, and primary content.
  • Appendix B: Measure Specifications provides information about how to generate each measure analyzed for the NHQR. Measures highlighted in the report are described, as well as other measures that were examined but not included in the text of the report.
  • Appendix C: Data Tables provides detailed tables for most measures analyzed for the NHQR, including measures highlighted in the report text and measures examined but not included in the text. A few measures cannot support detailed tables and are not included in the appendix.i

i NHQR data can now be accessed through NHQRDRnet, an online tool that provides Internet users with an opportunity to specify dimensions of analysis and produce data tables. NHQRDRnet is available through the AHRQ Web site at http://nhqrnet.ahrq.gov/.


 

Measure Set for the NHQR and NHDR

As in previous years, the 2008 reports focus on a subset of core report measures. In addition, composite measures are included to provide readers with a summarized picture of some aspect of health care by combining information from multiple component measures.

Core Measures

Core measures were first introduced in the 2005 reports. The Interagency Work Group selected a group of core measures from the full measure sets on which the reports would present findings each year. In 2006, the work group made additional changes to the core measure set. For some topics, the NHQR uses alternating sets of core measures. These measures, which relate to cancer prevention and childhood preventive services, are listed in Table 1.1.

Table 1.1. Alternating core measures

Reported in 2007 NHQR and NHDR*Reported in 2008 NHQR and NHDR
Breast cancer screening (mammography)Colorectal cancer screening
Breast cancer mortalityColorectal cancer mortality
Late-stage breast cancer diagnosisAdvanced stage colorectal cancer diagnosis
Children who received advice about healthy eatingChildren who received advice about physical activity
Children who had dental careChildren who had a vision check

* The measures listed in this column will be reported again in the 2009 reports.

All core measures fall into two categories: process measures, which track receipt of medical services, and outcome measures, which in part reflect the results of medical care. Both types of measures are not reported for all conditions due to data limitations. For example, data on HIV care are suboptimal; hence, no HIV process measures are included as core measures. In addition, not all core measures are included in trending analysis, because 2 or more years of data were not always available. A complete list of the 2008 NHQR core measure set is presented in Table 1.2.

Table 1.2. Core process and outcome measures

SectionProcess measuresOutcome measures
Effectiveness: Cancer
  • Adults age 50 and over who received colorectal cancer screening.
  • Colorectal cancer diagnosed at advanced stage
  • Colorectal cancer deaths
Effectiveness: Diabetes
  • Composite: Adults age 40 and over with diagnosed diabetes who received all three recommended services for diabetes in the calendar year (hemoglobin A1c measurement, dilated eye examination, and foot examination)a
  • Hospital admissions for lower extremity amputation per 1,000 population age 18 and over with diabetes
Effectiveness: End Stage Renal Disease
  • Dialysis patients who were registered on a waiting list for transplantation
  • Adult hemodialysis patients with adequate dialysis (urea reduction ratio 65% or greater)
Effectiveness: Heart Disease
  • Adult current smokers with a checkup in the last 12 months who received advice to quit smoking
  • Adults with obesity who ever received advice from a health provider to exercise more
  • Composite: Hospital patients with heart attack who received recommended hospital care (aspirin and beta blocker within 24 hours of admission, aspirin and beta blocker prescriptions at discharge, and smoking cessation counseling while hospitalized)b
  • Composite: Hospital patients with heart failure who received recommended hospital care (evaluation of left ventricular ejection fraction and ACE inhibitor or ARB prescription at discharge, if indicated, for left ventricular systolic dysfunction)b
  • Deaths per 1,000 adult hospital admissions with acute myocardial infarction (AMI)
Effectiveness: HIV and AIDS 
  • New AIDS cases per 100,000 population age 13 and over
Effectiveness: Maternal and Child Health
  • Women who completed a pregnancy in the last 12 months who first received prenatal care in the first trimester
  • Composite: Children ages 19-35 months who received all recommended vaccines
  • Children ages 3-6 who ever had their vision checked by a health provider
  • Children ages 2-17 for whom a health provider ever gave advice about the amount and kind of exercise, sports, or physically active hobbies they should have
  • Children ages 2-17 for whom a health provider ever gave advice about healthy eating
  • Infant deaths per 1,000 live births, birth weight <1,500 grams (No new data this year)
Effectiveness: Mental Health and Substance Abuse
  • Adults with major depressive episode in the last 12 months who received treatment for depression in the last 12 months
  • People age 12 and over who needed treatment for illicit drug use and who received such treatment at a specialty facility in the last 12 months
  • Suicide deaths per 100,000 population
Effectiveness: Respiratory Diseases
  • Adults age 65 and over who ever received pneumococcal vaccination
  • Composite: Hospital patients with pneumonia who received recommended hospital care (blood cultures collected before antibiotics are administered, initial antibiotic dose within 4 hours of hospital arrival and consistent with current recommendations, and influenza and pneumococcal screening or vaccination)c
  • Visits with antibiotics prescribed for a diagnosis of common cold per 10,000 population
  • People with current asthma who are now taking preventive medicine daily or almost daily
  • Patients with tuberculosis who completed a curative course of treatment within 1 year of initiation of treatment
Effectiveness: Nursing Home, Home Health, and Hospice Care
  • Long-stay nursing home residents with physical restraints
  • High-risk, long-stay nursing home residents with pressure sores
  • Short-stay nursing home residents with pressure sores
  • Adult home health care patients whose ability to walk or move around improved
  • Adult home health care patients who were admitted to the hospital
Patient Safety
  • Composite: Adult surgery patients who received appropriate timing of antibiotics
  • Adults age 65 and over who received potentially inappropriate prescription medications
  • Composite: Adult surgery patients with postoperative complications (postoperative pneumonia or venous thromboembolic event)d
  • Composite: Bloodstream infections or mechanical adverse events per 1,000 central venous catheter placements
Timeliness 
  • Adults who needed care right away for an illness, injury, or condition in the last 12 months who did not get care as soon as wanted
  • Emergency department visits in which patients left without being seen
Patient Centeredness
  • Composite: Adult ambulatory patients who reported poor communication with health providers
  • Composite: Children with ambulatory visits whose parents reported poor communication with health providers
 

a The specification for the time period for the eye examination measure was changed to include only the calendar year. For previous reports the early part of the subsequent year was also included.
b Use of angiotensin-converting enzyme (ACE) inhibitors in patients with left ventricular systolic dysfunction was changed to include angiotensin receptor blockers (ARBs) as an acceptable alternative. This change was also included in the 2007 report.
c Appropriate antibiotic selection was changed to exclude patients with health care-associated pneumonia from the denominator used in the calculation. Collection of samples for blood culture within 24 hours of hospital arrival was changed so that only those patients who were admitted to the intensive care unit within 24 hours of hospital arrival are included in the denominator. This change was also included in the 2007 report.
d The individual measure for postoperative urinary tract infection was refined to include only patients with catheter-associated urinary tract infections and, beginning this year, is no longer included in this composite measure.

Composite Measures

More than one measure can be combined to form a single composite measure of health care quality. A composite measure summarizes care that is represented by individual measures that are often related in some way, such as components of care for a particular disease or illness. Policymakers and others have voiced their support for composite measures because they can be used to facilitate understanding of information from many individual measures. The effort to develop new composites is ongoing and, in 2006, a number of new composite measures were added.ii The complete list of composite measures is shown in Table 1.3.

Composite measures in the NHQR are created based on two different models: the appropriateness model or the opportunities model. When possible, an appropriateness model is used to create composite measures. It is sometimes referred to as the "all-or-none" approach, because it is calculated based on the number of patients who received all appropriate care. One example of this model is the diabetes composite, in which a patient who receives only one or two of the three services would not be counted as having received the recommended care.

In other cases an opportunities model may be appropriate. The opportunities model assumes that each patient needs and has the opportunity to receive one or more processes of care, but not all patients need the same care. Composite measures that use this model summarize the proportion of appropriate care that is delivered. The denominator for an opportunities model composite is the sum of opportunities to receive appropriate care across a panel of process measures. The numerator is the sum of the components of appropriate care that are actually delivered. The composite measure of recommended hospital care for heart attack is an example where this model is applied. The total number of patients who actually receive treatments represented by individual components of the composite measure (e.g., aspirin therapy within 24 hours, beta blocker within 24 hours, and smoking cessation counseling) is divided by the sum of all of these opportunities to receive appropriate care.

Measures from the CAHPS® (Consumer Assessment of Healthcare Providers and Systems) surveys have their own method for computing composite measures that has been in use for many years. These composite measures average individual components of patient experiences of care. They are typically presented as the proportion of respondents who reported that providers sometimes or never, usually, or always performed well.

Composite measures that relate to rates of complications of hospital care are postoperative complications and complications of central venous catheters. For these complication rate composites, an additive model is used that sums individual complication rates. Thus, for these composites, the numerator is the sum of individual complications and the denominator is the number of patients at risk for these complications. The composite rates are presented as the overall rate of complications. The postoperative complications composite is a good example of this type of composite measure: If 50 patients had a total of 15 complications among them (regardless of their distribution), the composite score would be 30%.


ii Go to Chapter 1, Introduction and Methods, in the 2006 NHQR for more detailed information about these and other methods used to calculate composite measures used in the reports.


Table 1.3. Composite measures in the 2008 NHQR and NHDR (updated measures in italics)

Composite measureIndividual measures forming compositeModel
Receipt of three recommended services for diabetesa
  • Adults age 40 and over with diagnosed diabetes who had a hemoglobin A1c measurement in the calendar year.
  • Adults age 40 and over with diagnosed diabetes who had a dilated eye examination in the calendar yeara
  • Adults age 40 and over with diagnosed diabetes who had a foot examination in the calendar year.
Appropriateness
Childhood immunization
  • Children ages 19-35 months who received 4 doses of diphtheria-tetanus-pertussis vaccine
  • Children ages 19-35 months who received 3 doses of polio vaccine
  • Children ages 19-35 months who received 1 dose of measles-mumps-rubella vaccine
  • Children ages 19-35 months who received 3 doses of Haemophilus influenzae type B vaccine
  • Children ages 19-35 months who received 3 doses of hepatitis B vaccine
Appropriateness
Recommended hospital care for heart attackb
  • Hospital patients with heart attack who received aspirin within 24 hours of admission
  • Hospital patients with heart attack who were prescribed aspirin at discharge
  • Hospital patients with heart attack who received beta blocker within 24 hours of admission
  • Hospital patients with heart attack who were prescribed beta blocker at discharge
  • Hospital patients with heart attack and left ventricular systolic dysfunction who were prescribed ACE inhibitor or ARB at discharge
  • Smokers with heart attack who received smoking cessation counseling while hospitalized
Opportunities
Recommended hospital care for heart failureb
  • Hospital patients with heart failure who received an evaluation of left ventricular ejection fraction
  • Hospital patients with heart failure and left ventricular systolic dysfunction who were prescribed ACE inhibitor or ARB at discharge
Opportunities
Recommended hospital care for pneumoniac
  • Hospital patients with pneumonia who had blood cultures collected before antibiotics were administered
  • Hospital patients with pneumonia who received the initial antibiotic dose within 4 hours of hospital arrival
  • Hospital patients with pneumonia who received the initial antibiotic consistent with current recommendations
  • Hospital patients with pneumonia who received influenza screening or vaccination
  • Hospital patients with pneumonia who received pneumococcal screening or vaccination
Opportunities
Timing of antibiotics to prevent postoperative wound infection
  • Adult surgery patients who received prophylactic antibiotics within 1 hour prior to surgical incision
  • Adult surgery patients who had prophylactic antibiotics discontinued within 24 hours after surgery end time
Opportunities
Patient experience of care
  • Adult ambulatory patients whose providers sometimes or never listened carefully to them
  • Adult ambulatory patients whose providers sometimes or never explained things in a way they could understand
  • Adult ambulatory patients whose providers sometimes or never showed respect for what they had to say
  • Adult ambulatory patients whose providers sometimes or never spent enough time with them
  • Children with ambulatory visits whose parents report that their child's providers sometimes or never listened carefully to them
  • Children with ambulatory visits whose parents report that their child's providers sometimes or never explained things in a way they could understand
  • Children with ambulatory visits whose parents report that their child's providers sometimes or never showed respect for what they had to say
  • Children with ambulatory visits whose parents report that their child's providers sometimes or never spent enough time with them
CAHPS®
Postoperative complicationsd
  • Adult surgery patients with postoperative pneumonia events
  • Adult surgery patients with postoperative venous thromboembolic events
Additive
Complications of central venous catheters
  • Bloodstream infections per 1,000 central venous catheter placements
  • Mechanical adverse events per 1,000 central venous catheter placements
Additive

a The specification for the time period for the eye examination measure was changed to include only the calendar year. For previous reports the early part of the subsequent year was also included.
b Use of angiotensin-converting enzyme (ACE) inhibitors in patients with left ventricular systolic dysfunction was changed to include angiotensin receptor blockers (ARBs) as an acceptable alternative. This change was also included in the 2007 report.
c Appropriate antibiotic selection was changed to exclude patients with health care-associated pneumonia from the denominator used in the calculation. Collection of samples for blood culture within 24 hours of hospital arrival was changed so that only those patients who were admitted to the intensive care unit within 24 hours of hospital arrival are included in the denominator. This change was also included in the 2007 report.
d The individual measure for postoperative urinary tract infection was refined to include only patients with catheter-associated urinary tract infections and, beginning this year, is no longer included in this composite measure.

Presentation

As in past reports, the NHQR and its companion NHDR continue to be formatted as chartbooks. Each section in the 2008 report begins with a description of the importance of the section's topic in a standardized format. After introductory text, charts and accompanying findings highlight a small number of measures relevant to the topic. Sometimes these charts show contrasts by age when age data are available and relevant.

Almost all core measures and composite measures have multiple years of data, so figures typically illustrate trends over time. Figures include a notation about the reference population for population-based measures and about the denominator for measures based on services or events from provider-or establishment-based data collection efforts.

To place findings in the context of other Federal reporting initiatives, this report indicates where NHQR measures are also included in Healthy People 2010. Note that the Healthy People 2010 targets represented in the report figures, where applicable, reflect target values that were current when the reports were being prepared. Targets may be revised as new information becomes available. Therefore, the targets shown on the figures may differ from those in past reports or subsequent revisions. Also, Healthy People 2010 targets are only referenced in relation to the total population, not particular age groups. In addition, the data source for estimates reported here must be the same as the Healthy People 2010 data source in order for comparisons to be made.

Measures of effectiveness for each condition or care setting area are organized further into categories that reflect the patient's need for preventive care, treatment of illness, or management of chronic conditions. Further detail on each of these categories and the measures included can be found in Chapter 2, Effectiveness.

 

Databases Used in the 2008 Reports

Table 1.4 lists the databases used in the 2008 reports. This year the CPES is added to the set of databases that were used in the 2007 reports.

Table 1.4. Databases used in the 2008 reports (new databases in italics)

Survey data collected from populations

  • AHRQ, Medical Expenditure Panel Survey (MEPS), 2000-2005
  • Centers for Disease Control and Prevention (CDC), Behavioral Risk Factor Surveillance System (BRFSS), 2001-2006
  • CDC-National Center for Health Statistics (NCHS), National Health and Nutrition Examination Survey (NHANES), 1999-2006
  • CDC-NCHS, National Health Interview Survey (NHIS), 1998-2006
  • CDC-NCHS/ National Immunization Program, National Immunization Survey (NIS), 1998-2006
  • Centers for Medicare & Medicaid Services (CMS), Medicare Current Beneficiary Survey (MCBS), 1998-2004
  • National Center for Education Statistics, National Assessment of Adult Literacy, Health Literacy Component, 2003
  • National Hospice and Palliative Care Organization, Family Evaluation of Hospice Care, 2005-2007
  • National Institutes of Health (NIH), National Institute of Mental Health (NIMH), Collaborative Psychiatric Epidemiology Surveys (CPES), 2001-2003
  • Substance Abuse and Mental Health Services Administration (SAMHSA), National Survey on Drug Use and Health (NSDUH), 2002-2006
  • U.S. Census Bureau, American Community Survey, 2006

Data collected from samples of health care facilities and providers

  • American Cancer Society and American College of Surgeons, National Cancer Data Base (NCDB), 1999-2005
  • CDC-NCHS, National Ambulatory Medical Care Survey (NAMCS), 19972006
  • CDC-NCHS, National Hospital Ambulatory Medical Care Survey Emergency Department (NHAMCSED), 1997-2006
  • CDC-NCHS, National Hospital Ambulatory Medical Care Survey Outpatient Department (NHAMCSOPD), 1997-2006
  • CDC-NCHS, National Hospital Discharge Survey (NHDS), 1998-2006
  • CMS, End Stage Renal Disease Clinical Performance Measures Project (ESRD CPMP), 2001-2006

Data extracted from data systems of health care organizations

  • AHRQ, Healthcare Cost and Utilization Project (HCUP) Nationwide Inpatient Sample, 1994, 1997, 2000-2005, and State Inpatient Databases,a 2001-2005
  • CMS, Home Health Outcomes and Assessment Information Set (OASIS), 2002-2006
  • CMS, Hospital Compare, 2006

CMS, Medicare Patient Safety Monitoring System, 2004-2006

  • CMS, Nursing Home Minimum Data Set, 1999-2006
  • CMS, Quality Improvement Organization (QIO) program, Hospital Quality Alliance (HQA) measures, 2002-2006
  • HIV Research Network (HIVRN) data, 2003-2005
  • Indian Health Service, National Patient Information Reporting System (NPIRS), 2002-2005
  • National Committee for Quality Assurance, Health Plan Employer Data and Information Set (HEDIS®), 2001-2005
  • NIH, United States Renal Data System (USRDS), 1998-2004
  • SAMHSA, Treatment Episode Data Set (TEDS), 2002-2005

Data from surveillance and vital statistics systems

  • CDC-National Center for HIV, Viral Hepatitis, STD, and TB Prevention, HIV/AIDS Reporting System, 1998-2006
  • CDC-National Center for HIV, STD, and TB Prevention, TB Surveillance System, 1999-2004
  • CDC-National Program of Cancer Registries (NPCR), 2000-2004
  • CDC-NCHS, National Vital Statistics System (NVSS), 1999-2005
  • NIH-National Cancer Institute, Surveillance, Epidemiology, and End Results (SEER) program, 2000-2005

a Not all States participate in HCUP. For details, go to the HCUP entry in Appendix A, Data Sources.

Note: Measures from the American Community Survey and the National Assessment of Adult Literacy are used only in the 2008 NHDR. For details on these surveys, go to Chapter 1, Introduction and Methods, in the 2008 NHDR.

 

Continued Exploration of the Efficiency Dimension

The 2007 NHQR included an initial look at the concept of efficiency in the U.S. health care system. The 2008 NHQR continues this exploratory work by updating the discussion of topics introduced in 2007. Chapter 6, Efficiency, in this year's report also includes a first look at data on rehospitalizations for congestive heart failure for nine States in the United States. These nine States represent more than one-third of all hospitalizations for congestive heart failure.

 

Trend Analysis

This section discusses the methodology behind the median rates of change shown in Figures H.1 and H.3 in the Highlights chapter. The methodology differs from that used in previous reports. Readers are cautioned not to draw comparisons between rates of change in this and previous reports.

For each measure within a group (e.g., the group of core measures or the group of diabetes measures), the average annual rate of change was calculated between the earliest and the most recent estimates within a specified date range. Consistent with Health, United States, a formula that produces the geometric rate of change is used for this calculation for each measure.iii This geometric rate of change assumes the same rate of change each year between the two time periods. For each group the median rate of change is determined, based on the rates of change for the measures within that group.

Specifying the optimal time period for analysis without excluding large numbers of measures has been a challenge. Specific issues include:

  • Changes in the measure set over time.
  • Changes in the data source over time.
  • Lack of availability of data for particular data years.
  • Recalculation of prior years' data.

Changes in the measure set may result from the deletion of measures due to a lack of availability of new data or a determination by the NHQR's Interagency Work Group that a measure no longer meets its criteria for inclusion. Changes also result from the addition of a measure. For example, this year's report includes a new core measure for daily use of preventive medicine for current asthma. This measure uses data from AHRQ's Medical Expenditure Panel Survey (MEPS). Data for this measure were first collected in 2003. The latest MEPS data year available at the time this report was submitted for review was 2005. Therefore, for this measure data are only available for 3 years: 2003, 2004, and 2005. A 5-year or longer period might be available for other measures.

For this and other reasons (e.g., variability of collection schedules among the different data sources used by the NHQR), if a strict time-interval criterion for trend analysis were used (e.g., only the 2000 and 2005 data years), a large number of measures would be excluded. The approach taken for this year's report favors inclusion of as many measures as possible over a strict application of a minimum number of data points or time interval.

For the trend analysis, 2 data years for each measure are used. In addition, a more inclusive approach to data availability is taken. A data availability preference hierarchy is applied as follows:

  • Take the latest data year available for a particular measure (e.g., 2006 or 2005).
  • Attempt to find data for a 5-year interval (e.g., if 2006 is the latest data year available, then select 2001 as the early data year).
  • If no valid data are available for that year, then attempt to find data for a 4-year interval.
  • Continue this process of reducing the year interval until valid data are selected.

iii Go to the entry for Average Annual Rate of Change in Appendix II, Definitions and Methods, Health, United States, 2007. Available at: http://www.cdc.gov/nchs/hus.htm.


Starting with the latest data year available ensures that up-to-date information is not excluded from the analysis (e.g., 2006 data from the National Health Interview Survey). For most core measures, the trend analysis will use estimates based on a 5-year interval. But, as shown above for the asthma medication measure, application of the preference hierarchy will result in the selection of estimates from 2003 and 2005 (because data from 2000-2002 are not available). Note also that, for alternating measures, the process described above is applied to each measure so that both are included.

For some data sources, data may be available for a 5-year interval, but changes in data collection or analytic methodology may render comparisons between 2 data years invalid. For example, beginning in 2005, the data collection method for the Medicare Quality Improvement Organization (QIO) Program changed from the abstraction of randomly selected Medicare beneficiary records to the receipt of hospital self-reported data for all payer types. Therefore, only 2005 and 2006 QIO data are included in the trend analysis. Although not optimal, this approach is preferable to comparing data with different denominators and collection methods or to excluding QIO measures from the analysis.

In some cases, it is possible to reanalyze the data from prior data years if a change occurs that might otherwise make a comparison invalid. For example, a number of patient safety measures discussed in Chapter 3, Patient Safety, make use of AHRQ's Patient Safety Indicator software. For this year's report, version 3.1 of the software was used. This version was not available when the data for prior reports were generated. It was possible, however, to reanalyze prior data years using the new version of the software so that a 5-year data interval was available for the trend analysis.

One other methodological issue should be noted. Composite measures are included in the core measure category. To avoid duplication of estimates within the other categories, composite measures are not included in other categories where estimates from their component measures are used. For example, the diabetes composite measure (which includes HbA1c measurement, eye exam, and foot exam) contributes to the overall rate for the core measures group but not to the diabetes group rate, which uses the estimates from the three noncore component measures.

In addition to the trend analysis for groups of measures shown in the Highlights chapter, each section of Chapter 2, as well as the following chapters, details changes over time for individual measures. For each measure discussed in the reports, two criteria are applied to determine whether a significant trend exists:

  • First, the difference between the earliest and most recent estimates shown must be statistically significant at p<0.05.
  • Second, the average (mean) annual rate of change must be at least 1%.

Only changes over time that meet these two criteria are discussed in the 2008 reports as indicating a change over time or between population subgroups.

Various words and phrases might be used to refer to a change, depending on the specific measure being discussed. For example, "more likely to," "significantly below," "decreased," "had the highest rate," "change," "improvement," "statistically higher," and "less likely to" all refer to changes that meet the two criteria listed above. Although the explicit use of the term "statistically significant" is warranted in some cases, imposing its use in every sentence where a change is discussed would be overly cumbersome. Also, not every significant change among data years or populations is noted. Therefore, no conclusions should be drawn if a numeric difference in a figure is not referenced in the corresponding text or bullet.

Due to the methodological changes discussed here, changes to estimates for data from prior years, and changes to the measure set, it is not appropriate to compare the rates of change for measure groups discussed in this year's report with those from prior years.

Finally, this report conforms to the Government Printing Office Style Manual. In some cases, terms or spelling may vary to reflect an original data source or an agency or program name. For example, "health care" usually appears as two words but may appear as one word in an agency name, such as the Agency for Healthcare Research and Quality. These minor variations in spelling and usage do not alter the meaning or intent of the data and are purely cosmetic in nature.

Current as of March 2009
Internet Citation: Chapter 1. Introduction and Methods: National Healthcare Quality Report, 2008. March 2009. Agency for Healthcare Research and Quality, Rockville, MD. http://www.ahrq.gov/research/findings/nhqrdr/nhqr08/Chap1.html