In Utah and Colorado in 1992, the proportion of hospital admissions due to an adverse event in ambulatory care was 0.476% resulting in 2608 AAEs. The proportion of hospital admissions resulting from a preventable adverse event in ambulatory care was 0.211% resulting in 1296 APAEs. When extrapolated to all US discharges (approximately 36
000 hospital discharges annually in the US) the estimated annual number of hospital admissions resulting from an adverse event in ambulatory care is 171
360. This number is higher than the total number of admissions for phlebitis, thrombophlebitis and thromboembolism, or for abdominal hernia.10
The national estimated number of annual hospital admissions resulting from preventable adverse events in ambulatory care is 75
858. Of these events, 10% led to serious permanent harm or death. Hospital‐admission‐related preventable adverse events in ambulatory care result in more hospital admissions than HIV infection, or cervical and uterine cancer combined.10
Of the admissions in which a preventable adverse event in an outpatient setting occurred, extrapolated nationally, this resulted in 4839 serious permanent injuries and 2587 deaths.
Not surprisingly, physician's offices and emergency rooms, the most common settings for ambulatory care, were the settings for the most (75%) preventable ambulatory adverse events. Similarly, general medicine internists and family physicians, representing nearly 30% of all US physicians,11,12
were the types of physicians most often involved in the occurrence of preventable events. These clinicians were involved in about one‐third of the ambulatory preventable adverse events followed by an even distribution of preventable ambulatory adverse events among medical and surgical specialists and emergency medicine physicians. The types of preventable events were evenly distributed among diagnostics, surgical and medical procedures, medication, and incorrect or delayed treatments.
These data suggest that a wide array of strategies may be needed to reduce ambulatory adverse events. An initial focus on diagnostic errors in office‐based general internal medicine and family practice may be warranted. It is not surprising that the multifaceted nature of processes in primary care practice including preventive screening, diagnosis and treatment of acute and chronic problems, and health promotion activities can lead to errors that can lead to significant harm. Previous research has identified specific aspects of primary care that could lead to diagnostic errors. For example, missing clinical information is common in the coordination of the care.13
Appointment scheduling, chart management, and follow‐up of test results are additional important steps in the coordination the of care process for which errors and related injuries are common.14
Several studies point to the challenges of laboratory testing and imaging processes in ambulatory care. Hickner et al
reported that laboratory tests and imaging studies were ordered during 29–38% of clinical encounters and that between 15% and 54% of errors reported by office‐based physicians and staff were related to these processes.15
Nutting et al
reported that problems with laboratory testing in primary care physician offices occurred in 1.1 per 1000 patient visits16
and, that the communication of test results was also frequently problematic. Studies of clinicians' perceptions of laboratory and imaging processes have shown that most primary care clinicians are not satisfied with their methods of tracking abnormal results,17
report that delays in results are common18
and that follow‐up care is suboptimal.15,19
In addition, although a key activity in primary care is the provision of preventive care, appropriate preventive screening was shown to occur in only 55% of the visits for which screenings were indicated.7
This study suggests that ambulatory care diagnostic events can result in high levels of harm. Process improvement activities to increase the reliability of tracking and communicating critical laboratory values are underway in hospital‐based contexts and could potentially be applied to ambulatory care.20
Medication safety is another area of importance in primary care21,22
and, as shown in this study, medication‐related preventable ambulatory adverse events are common. Use of technology, particularly computerised physician order entry systems, has been recommended to deal with many of the challenges of medication safety in hospital‐based contexts, but such systems are not, as yet, common in ambulatory care settings. Medication reconciliation is also being recommended for ambulatory care, however, there are many additional documented medication safety risks that will remain unresolved even with effective implementation of these interventions, such as look‐alike/sound‐alike medications23
and adequate patient education.24
Both medication factors and patient‐related factors have been shown to contribute to medication safety risks24
and many older patients in this study were found to have experienced medication events in the home.
Preventable ambulatory adverse events related to surgery and other procedures comprised more than one‐third of all events and resulted in the highest level of harm to patients. The frequency of such events may now be significantly higher considering that the number of ambulatory care surgeries and procedures has increased annually since 1992 (year of data collection). Currently, 60% of elective surgical procedures in the US occur in an outpatient setting.25
The findings in this study also support previous findings in which hospitalisation within 7 days of an ambulatory surgery occurred in 9.08 per 1000 patients and the death rate of patients from ambulatory surgery was 35 per 100
Although there has been significant patient safety improvement activity in hospital‐based care, relatively fewer patient safety interventions have been adopted in ambulatory care surgery and office‐based contexts. Increased research and monitoring of ambulatory surgery and procedures (in both ambulatory surgery centres and physician offices) may be needed.
The Institute of Medicines report27
estimated from the data used in this study that 44
000 deaths occur annually in the US that are attributable to preventable adverse events. Of these 44
000 deaths 5.50% occurred as a result of a preventable adverse event in ambulatory care settings, resulting in an estimated 2419 APAE deaths in the US annually.