Skip Navigation U.S. Department of Health and Human Services
Agency for Healthcare Research Quality
Archive print banner

Reducing Errors in Health Care

This information is for reference purposes only. It was current when produced and may now be outdated. Archive material is no longer maintained, and some links may not work. Persons with disabilities having difficulty accessing this information should contact us at: Let us know the nature of the problem, the Web address of what you want, and your contact information.

Please go to for current information.

Translating Research Into Practice

Medical errors are responsible for injury in as many as 1 out of every 25 hospital patients; an estimated 48,000-98,000 patients die from medical errors each year. Errors in health care have been estimated to cost more than $5 million per year in a large teaching hospital, and preventable health care-related cost the economy from $17 to $29 billion each year.

Agency for Healthcare Research and Quality (AHRQ) research has shown that medical errors may result most frequently from systems errors—organization of health care delivery and how resources are provided in the delivery system.

Patients at Risk / How Errors Occur / Improving Patient Safety / Promoting Safety / References

Patients at Risk

Medical errors may result in:

  • A patient inadvertently given the wrong medicine.
  • A clinician misreading the results of a test.
  • An elderly woman with ambiguous symptoms (shortness of breath, abdominal pain, and dizziness) whose heart attack is not diagnosed by emergency room staff.

Errors like these are responsible for preventable injury in as many as 1 out of every 25 hospital patients1.

Errors in health care have been estimated to cost more than $5 million per year in a large teaching hospital2. According to a recent report by the Institute of Medicine (IOM)3, preventable health care-related injuries cost the economy from $17 to $29 billion annually, of which half are health care costs.

The IOM report3 estimates that 44,000 to 98,000 people each year die from medical errors. Even the lower estimate is higher than the annual mortality from motor vehicle accidents (43,458), breast cancer (42,297), or AIDS (16,516), thus making medical errors the eighth leading cause of death in the United States.

These and other findings of the IOM report are based on research sponsored by a variety of organizations, including the Agency for Healthcare Research and Quality (AHRQ).

For example, a study by AHRQ4 found that just one type of error—preventable adverse drug events—caused one out of five injuries or deaths per year to patients in the hospitals that were studied.

Return to Contents

How Errors Occur

Errors can occur at any point in the health care delivery system, AHRQ-supported research has revealed.

Medication Errors

These are preventable mistakes in prescribing and delivering medication to patients, such as prescribing two or more drugs whose interaction is known to produce side effects or prescribing a drug to which the patient is known to be allergic.

Research by AHRQ-supported investigators is helping to characterize these errors (called preventable adverse drug events, or ADEs) and suggest how to prevent them.

  • In a study of inpatient care in two tertiary care hospitals5, errors in ordering and administering medicines accounted for 56 and 34 percent, respectively, of preventable adverse drug events.
  • Findings from a second study6 showed that dosage errors, in particular, were primarily due to the physician's lack of knowledge about the drug or about the patient for whom it was prescribed.
  • An attempt to identify risk factors for preventable adverse drug reactions among patients admitted to medical and surgical units at two large hospitals7 found few such factors, which suggested to the researchers that a focus on improving medication systems would prove more effective.

Surgical Errors

In contrast to ADEs, surgical adverse events (1 in 50 admissions in Colorado and Utah hospitals during 1992)8, accounted for two-thirds of all adverse events and 1 of 8 hospital deaths in a recent retrospective study of these institutions by an AHRQ fellow.

Diagnostic Inaccuracies

Incorrect diagnoses may lead to incorrect and ineffective treatment or unnecessary testing, which is costly and sometimes invasive. Also, inexperience with a technically difficult diagnostic procedure can affect the accuracy of the results. Here, too, AHRQ-funded researchers have made major contributions.

  • One study9 showed that physicians who performed 100 or more colposcopies (a test used to follow up abnormal Pap smears) a year had more accurate findings than physicians who performed the procedure less often.
  • Another study10 demonstrated that measuring blood pressure with the most commonly used type of equipment often gives incorrect readings that may lead to mismanagement of hypertension.

System Failures

Although errors in medication, surgery, and diagnosis are the easiest to detect, medical errors may result more frequently from the organization of health care delivery and the way that resources are provided to the delivery system. Research by AHRQ-supported scientists is helping to identify the systemic factors contributing to preventable adverse events.

  • Investigators in a major study6 discovered that failures at the system level were the real culprits in over three-fourths of adverse drug events.
  • Failures in disseminating pharmaceutical information, in checking drug doses and patient identities, and in making patient information available are system errors that accounted for adverse drug events in over half of the hospitals studied.
  • One system-level factor, staffing levels of nurses (adjusted for hospital characteristics), was found in a study11 to influence the incidence of adverse events following major surgery, such as urinary tract infections, pneumonia, thrombosis, and pulmonary compromise.

This research on systemic problems leads investigators to conclude that any effort to reduce medical errors in an organization requires changes to the system design, including possible reorganization of resources by top-level management.

Return to Contents

Improving Patient Safety

Research funded by AHRQ and others has been important in identifying the extent and causes of errors. Now, additional research is needed to develop and test better ways to prevent errors, often by reducing the reliance on human memory. Some areas of past research that have shown promise in helping to reduce errors include computerized ADE monitoring, computer-generated reminders for followup testing, and standardized protocols.

Computerized ADE Monitoring

Although chart review was found in an AHRQ-funded study12 to be more accurate than computer tracking and voluntary reporting in identifying adverse drug events, it required five times more personnel time. Researchers concluded that the computerized method was the most efficient means of tracking drug errors.

Computer-Generated Reminders for Followup Testing

Some diagnostic tests must be repeated to follow up certain conditions, but a small number of such repeat tests are done too early to yield useful results. In contrast, laboratory results showing that a patient needs critical care may not be communicated in a timely manner.

  • One study funded by AHRQ13 found that a computerized reminder system to alert physicians to the proper timing of repeat tests reduced the number of patients who were subjected to unnecessary repeat testing.
  • The same research group subsequently reported14 that an automatic alerting system for communicating critical laboratory results reduced the time until appropriate treatment when compared with the existing hospital paging system.

Standardized Protocols

An AHRQ-sponsored study15 of patients in intensive care units who had severe respiratory disease found a four-fold increase in survival rate with the use of computerized treatment protocols.

Still other investigators are testing computerized decision support systems in various patient populations. All of these research efforts reflect AHRQ's commitment to improving patient safety by providing new tools to augment provider judgment.

AHRQ-funded research continues to create and test methods to help clinicians avoid errors in health care delivery. An investigation funded by AHRQ and the National Institute on Aging will address the incidence and preventability of adverse drug events in elderly patients receiving ambulatory care.

The Agency has recently funded four Centers for Education and Research in Therapeutics (CERTs)16 as part of a 3-year demonstration program. The CERTs will conduct research to increase understanding of ways to improve the appropriate and effective use of drugs, biologicals, and devices in treatments and to avoid adverse events. These centers will also add to our knowledge of the possible risks of new uses of drugs, and combinations of drugs, as they are prescribed in everyday practice.

In addition, the Agency has recently announced17 that it will enter into cooperative agreements with nonprofit and for-profit health care organizations to test the effectiveness of the transfer and application of systems-based best practices to reduce medical errors and improve patient safety. This research will help identify high-risk patients or patient groups, providers, health care processes and settings, as well as developing generalizable methods for error reduction.

Return to Contents

Promoting Safety

AHRQ (then known as AHCPR, the Agency for Health Care Policy and Research) supported the conference "Enhancing Patient Safety and Reducing Errors in Health Care," which launched the National Patient Safety Foundation.

AHRQ also works with partners, such as the National Committee on Patient Information and Education (NCPIE), to promote patient awareness of medication safety. In 1997, AHCPR and NCPIE co-sponsored the publication of a consumer guide, Prescription Medicines and You, to help consumers understand how to avoid errors in taking medicines.

Currently, AHRQ serves as the lead agency on medical errors within the Quality Interagency Coordination Task Force (known as the QuIC), which developed the Federal response to the IOM report.

In sum, AHRQ's contributions have resulted in a broader understanding of the nature of patient safety problems and where they occur in the delivery of health care. AHRQ-supported research is in the forefront of a rethinking of health care systems to reduce medical errors.

More information on AHRQ medical errors research is online. You also may contact:

Karen Migdail
AHRQ Public Affairs
540 Gaither Road, Suite 2000
Rockville, MD 20982
(301) 427-1855 or 427-1853

Return to Contents


1. Brennan TA, Leape LL, Laird NM, et al. Incidence of adverse events and negligence in hospitalized patients: Results of the Harvard Medical Practice Study I. N Engl J Med 1991;324:370-6. Abstract.

2. Bates DW, Spell N, Cullen DJ, et al. The costs of adverse drug events in hospitalized patients. JAMA 1997;277(4):307-11. Abstract.

3. Institute of Medicine. To Err is Human: Building a Safer Health System. Washington, D.C.: National Academy Press; 1999. Publication.

4. Leape LL, Brennan TA, Laird N, et al. The nature of adverse events in hospitalized patients. Results of the Harvard Medical Practice Study II. N Engl J Med 1991;324:377-84. Abstract.

5. Bates D, Cullen DJ, Laird N, et al. Incidence of adverse drug events and potential adverse drug events. JAMA 1995;274(1):29-34. Abstract.

6. Leape LL, Bates DW, Cullen DJ, et al. Systems analysis of adverse drug events. JAMA 1995; 274(1):35-43. Abstract.

7. Bates DW, Miller EB, Cullen DJ, et al. Patient risk factors for adverse drug events in hospitalized patients. Arch Intern Med 1999;159:2553-60. Abstract.

8. Gawande AA, Thomas EJ, Zinner MJ, et al. The incidence and nature of surgical adverse events in Colorado and Utah in 1992. Surgery 1999;126(1):66-75. Abstract.

9. Gordon P. Diagnostic accuracy of community physicians performing colposcopy. AHCPR Grant HS07162 Final Report; 1996.

10. Hla KM. Impact of errors in blood pressure measurement. AHCPR Grant HS07301 Final Report; 1994.

11. Kovner C, Gergen PJ. Nurse staffing levels and adverse events following surgery. Image J Nurs Sch 1998;30(4):315-21. Abstract.

12. Jha AK, Kuperman GJ, Teich JM, et al. Identifying adverse drug events: Development of a computer-based monitor and comparison with chart review and stimulated voluntary report. J Am Med Inform Assoc 1998;5(3):305-14. Abstract.

13. Bates DW, Kuperman GJ, Rittenberg E, et al. A randomized trial of a computer-based intervention to reduce utilization of redundant laboratory tests. Am J Med 1999;106(2):144-50. Abstract.

14. Kuperman GJ, Teich JM, Tanasijevic MJ, et al. Improving response to critical laboratory results with automation: Results of a randomized controlled trial. J Am Med Inform Assoc 1999;6(6):512-22. Abstract.

15. Morris AH. Protocol management of adult respiratory distress. New Horizons 1993;1(4):593-602. Abstract.

16. AHCPR launches research program to improve the safe and effective use of medical products. [News story] Research Activities Oct 1999;230:15.

17. Agency for Healthcare Research and Quality. Systems-related best practices to improve patient safety. [Request for Applications]. Dec 16, 1999. http//

Return to Contents

AHRQ Publication No. 00-PO58
Replaces AHCPR Publication No. 98-PO18
Current as of April 2000


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


AHRQ Advancing Excellence in Health Care