Reporting of Adverse Drug Events: Examination of a Hospital Incident Reporting System

Introduction

Hospitals and health care providers strive to deliver the safest care possible. Nevertheless adverse drug events are common,^1–4 often preventable,^5–9 and costly.^10–15 Preventable adverse drug events occur due to medication errors, which include errors in the process of ordering or delivering a medication and errors of omission (e.g., failing to administer a drug as prescribed). Bates et al.^{16, 17} estimated that approximately 1 percent of medication errors result in adverse drug events. Minimizing or eliminating medication errors is vital to improve patient safety and the quality of hospital care. Medication error reporting is an essential component of achieving these goals.

Several national voluntary and mandatory reporting systems exist for medication errors, adverse events, and medical device problems in the United States.^8–22 The Institute of Medicine called for national mandatory reporting to State departments of health of events that result in death or serious harm, and voluntary reporting within health care organizations of less serious events.^{19, 23–27} The Institute for Safe Medical Practices, however, has endorsed voluntary reporting of adverse drug events.^{23, 24, 26} Although the debate regarding the need for voluntary or mandatory reporting systems continues,^{23–25, 28–32} voluntary reporting systems are more appealing to institutions and are potentially valuable sources of information that hospitals could use for systemwide improvements.³³

Previous research on voluntary incident reporting involved examining reports on a restricted number of patient care units for limited time periods, typically less than 1 year.^34–39 To better understand how to enhance incident reporting, it is essential to examine the existing state of reporting, particularly voluntary systems. This study analyzed a hospitalwide voluntary incident reporting system at an academic teaching hospital during a 22-month time period. Specifically, this study aimed to determine the extent and variation in the reporting of potential and preventable adverse drug events by comparing incident reporting with other information sources, such as pharmacist reporting of events.

Methods

Results

Overall reporting of events in RMEES and PHRED

There were 94,445 admissions and 483,845 patient days during the 22-month study period. A total of 228 preventable adverse drug events and 898 potential adverse drug events were reported into RMEES during this time. There were 51 unique units (six ICUs, four observation units, and 41 nursing divisions) that reported potential and/or preventable adverse drug events into RMEES. Among the 51 units, one (2 percent) reported no potential adverse drug events, while four (7.8 percent) reported no preventable adverse drug events. Radiology accounted for 31 out of 43 preventable adverse drug events (72 percent) that occurred outside of patient care areas and were classified as “other.”

Only 21 units reported preventable adverse drug events into PHRED during the study period. Approximately 6 percent of events (1,196) did not specify a nursing unit; all of these involved potential adverse drug events. Of the 51 units, two (3.8 percent) reported no potential adverse drug events, while 58 percent of the units reported no preventable adverse drug events into PHRED.

Table 1

Overall reporting of adverse drug events at (more...)

Table 1

Overall reporting of adverse drug events at Barnes—Jewish Hospital: rates per 1,000 patient days

Adverse drug events	RMEES number of events (rate*)	PHRED number of events (rate*)	Total number of events (rate*)
Preventable	228 (0.47)	40 (0.08)	268 (0.55)
Potential	898 (1.85)	20,115 (41.5)	21,013 (43.43)
Total (potential + preventable)	1,126 (2.32)	20,155 (41.6)	21,281 (43.9)

*

Rate per 1,000 patient days

Table 1 describes the total preventable and potential adverse drug event reporting rates per 1,000 patient days at BJH from both RMEES and PHRED. There were no common preventable adverse drug events between RMEES and PHRED, implying that the two systems capture uniquely independent events. Consequently, the total preventable adverse drug event rate (0.55) reflects the total rate from both systems. On the other hand, potential adverse drug events were not examined to identify common events between the two systems. Based on the presumption that there is minimal overlap in the events reported in RMEES and PHRED, the best upper-limit estimate (in case there were no common events) of the potential adverse drug event rate is the total potential adverse drug event rate of 43.4 per 1,000 patient days, with the lower limit of this estimate (in case all events were common) being the PHRED rate (41.5 per 1,000 patient days). Total potential adverse drug event rates from both RMEES and PHRED were noticeably higher than preventable adverse drug event rates. RMEES had a considerably lower total adverse drug event (potential + preventable) reporting rate per 1,000 patient days than PHRED.

Description of preventable adverse drug events in RMEES and PHRED

Table 2

Description of the most frequently reported (more...)

Table 2

Description of the most frequently reported preventable adverse drug events in RMEES and PHRED

Event classifications	RMEES (N = 228) n (%)	PHRED (N = 40) n (%)	Total (N=268) n (%)
Drug classes
CNS agents	47 (22.8)	11 (27.5)	58 (21.6)
Blood formation and coagulation agents	37 (16.2)	7 (17.5)	44 (16.4)
Hormones and synthetics	31 (15.0)	1 (2.5)	32 (11.9)
Radiologic contrast	30 (13.2)	0 (0.0)	30 (11.1)
Anti-infectives	24 (10.5)	4 (10.0)	28 (10.4)
Cardiovascular agents	23 (10.1)	10 (25.0)	33 (12.3)
Other	36 (15.7)	7 (17.5)	43 (16.0)
Type of event
Wrong dose	37 (15.8)	5 (12.5)	42 (15.6)
Wrong drug	32 (14.0)	8 (20.0)	40 (14.9)
Wrong infusion rate	31 (13.6)	5 (12.5)	36 (13.4)
Extra dose	30 (13.2)	5 (12.5)	35 (13.0)
Missed dose	20 (8.8)	5 (12.5)	25 (9.3)
IV infiltrations	17 (7.5)	0 (0)	17 (6.3)
Wrong patient	16 (7.0)	2 (5.0)	18 (6.7)
Other	46 (20.17)	10 (25.0)	56 (20.9)
Event reason
Administration	89 (39.0)	8 (20.0)	97 (36.2)
Device use	44 (19.3)	5 (12.5)	49 (18.3)
IV error	17 (7.5)	0 (0)	17 (6.3)
Transcription error	17 (7.5)	10 (25.0)	27 (10.0)
Prescribing error	13 (5.7)	8 (20.0)	21 (7.8)
Charting error	10 (4.4)	5 (12.5)	15 (5.6)
Other	37 (16.2)	4 (10.0)	41 (15.3)

Table 2 describes the most frequent preventable adverse drug events reported in RMEES and PHRED. Similar proportions of events were reported in the two reporting systems for most drug classes, event types, and event reasons. No single drug class or event type was predominantly reported in either RMEES or PHRED. In both RMEES and PHRED, medication administration errors due to slip or memory lapse were among the most common reasons for the events.

In RMEES, the drugs most frequently reported involving preventable adverse drug events were heparin, insulin, vancomycin, and morphine (all from the top four drug classes of RMEES), while the drugs most frequently involved in PHRED events were diltiazem, heparin, and propofol (from the top three drug classes of PHRED). Insulin was not reported in any of the PHRED events. More than 50 percent of the preventable adverse drug events in RMEES were associated with just 14 drugs, while no such pattern was noted for the drugs involved in PHRED events. Events involving cardiovascular agents were more common in PHRED events. No PHRED reports involved IV infiltrations from radiologic contrast dyes or other medications. Overall, almost one-third (30 percent) of the preventable adverse drug events reported by nurses in RMEES were related to medication administration errors, while the majority of pharmacist-reported PHRED events were associated with transcription errors.

Comparison of drug classes and event types for RMEES- and PHRED-reported events

Table 3

Event type versus drug class from RMEES and (more...)

Table 3

Event type versus drug class from RMEES and PHRED

	Drug Class n (%)*
Event Type	CNS agents	Blood formation & coagulation agents	Cardiovascular agents	Hormones & synthetics	Anti-infectives	Electrolyte caloric & water balance	Other	Total N (% of total)
Wrong dose	18 (45)	4 (10)	3 (8)	8 (20)	0 (0)	1 (3)	6 (15)	40 (17)
Wrong drug	11 (28)	1 (3)	6 (15)	6 (15)	5 (13)	6 (15)	5 (12)	40 (17)
Wrong Infusion rate	2 (6)	22 (63)	0 (0)	2 (6)	1 (3)	2 (6)	6 (17)	35 (15)
Extra dose	8 (23)	7 (20)	10 (29)	3 (9)	3 (9)	2 (6)	2 (6)	35 (15)
Missed dose	5 (20)	2 (8)	5 (20)	5 (20)	4 (16)	3 (12)	1 (4)	25 (11)
IV infiltrations	0 (0)	1 (17)	0 (0)	0 (0)	4 (67)	0 (0)	1 (17)	6 (3)
Wrong patient	4 (22)	1 (6)	4 (22)	6 (33)	1 (6)	1 (6)	1 (6)	18 (8)
Wrong Administration mode †	2 (11)	1 (6)	2 (11)	1 (6)	9 (50)	3 (17)	0 (0)	18 (8)
Other	5 (24)	3 (14)	3 (14)	1 (5)	1 (5)	2 (10)	6 (29)	21 (9)
	55 (23)	42 (18)	33 (14)	32 (13)	28 (12)	20 (8)	28 (12)	238 (100)

*

N (percent of row total). Percentages may not add to 100 due to rounding.

†

Wrong administration mode includes wrong time, wrong route, and wrong frequency.

‡

Thirty preventable adverse drug events reported only in the AER system that involved radiologic contrast dyes were not included in the above table.

The majority of the events associated with the radiologic contrast dyes were IV infiltrations (36%) and adverse reactions (27%).

Table 3 compares the drug classes with the various event types for the events reported in RMEES and PHRED. Dosing errors (wrong dose, extra dose, missed dose) were the predominant types of events reported. Almost half (44.4 percent) of the wrong dose events were related to central nervous system agents, primarily morphine. More than 50 percent of the wrong infusion rate events were associated with heparin. Insulin was associated with multiple types of events and accounted for all of the wrong dose, wrong drug, wrong infusion rate, missed dose, and wrong patient events within the “hormones and synthetics” class.

Extent of reporting in RMEES and PHRED

Table 4

Reported rates (per 1,000 patient days) of (more...)

Table 4

Reported rates (per 1,000 patient days) of adverse drug events (ADEs) and alerts by service: RMEES and PHRED

	Rate (number of events) by service*
	Medicine	Surgery	Obstetrics	Psychiatry	Rehab
RMEES system
Potential ADEs	1.33 (342)	2.35 (391)	1.03 (26)	1.64 (46)	1.30 (14)
Preventable ADEs	0.41 (107)	0.37 (62)	0.12 (3)	0.39 (11)	0.18 (2)
Total ADEs	1.74 (449)	0.37 (453)	1.15 (29)	2.04 (57)	1.49 (16)
PHRED
Potential ADEs	42.79 (10982)	44.64 (7412)	0.47 (12)	17.90 (500)	1.21 (13)
Preventable ADEs	0.09 (24)	0.1 (16)	0	0	0
Total ADEs	42.89 (11006)	44.74 (7428)	0.47 (12)	17.90 (500)	1.21 (13)
Pharmacy Expert System
Alert rate per 1,000 pt days	7.97 (2046)	6.76 (1123)	0.27 (7)	0.93 (26)	0.84 (9)

*

Patient days not available for “other” service category, containing 79 (8.8%) potential adverse drug event reports, 43 (17.9%) preventable adverse drug event reports in the AER system, and 1,197 (6%) PHRED reports.

Table 4 describes the reported rates (per 1,000 patient days) of potential and preventable adverse drug events by service for events reported in RMEES and PHRED and the pharmacy expert systems. There was considerable variation in the reported total adverse drug event rates per 1,000 patient days across the various services in both RMEES and PHRED. In RMEES, significant differences by service were noted for reported potential adverse drug event rates per 1,000 patient days (P < 0.001). Surgery had a significantly higher potential adverse drug event rate (2.35) than medicine (1.33) and obstetrics (1.03). Reported rates (per 1,000 patient days) of preventable adverse drug events did not differ significantly by service.

In PHRED, the potential adverse drug event rates per 1,000 patient days for the various units varied from 0 to 158 (median = 15) while the preventable adverse drug event rates per 1,000 patient days among the various units varied from 0 to 0.66 (median = 0). Significant differences by service were noted for reported potential adverse drug event rates per 1,000 patient days (P < 0.001). Surgery had a marginally, though statistically significant, higher potential adverse drug event reporting rate per 1,000 patient days (44.7) than medicine (42.7); both services had much higher reporting rates than psychiatry (17.9), rehabilitation services (1.21), and obstetrics (0.47) (P < 0.001). Preventable adverse drug event rates per 1,000 patient days did not differ significantly by service in PHRED.

Variation in reporting between potential and preventable adverse drug events in RMEES

Figure 1. Scatter plot of RMEES potential (more...)

   Figure 1. Scatter plot of RMEES potential adverse drug event rates versus preventable adverse drug event rates per 1,000 patient days, by service

Figure 1 depicts the adverse drug event reporting variation among patient care units that use RMEES. There was a modest relationship (R² = 0.27) between the reported potential and preventable adverse drug rates in RMEES across all services. There was no relationship (R² = 0.002) between potential and preventable adverse drug event reporting rates in PHRED. The potential adverse drug event rates varied from 0.00 to 13.3 (median = 1.4), while the preventable adverse drug event rates varied from 0.00 to 3.15 (median = 0.37). The ratio of potential adverse drug events to preventable adverse drug events across the various units in RMEES varied from 0 to 16 (median = 4.5).

Units in the medicine service had the highest variation in potential adverse drug event reporting rates per 1,000 patient days (range 0.19 to 13.32), followed by surgery (range 0.67 to 9.46). Four surgery units and one obstetrics unit reported only potential adverse drug events (no preventable adverse drug events). On the other hand, surgical units had the highest variation in preventable adverse drug event reporting rates per 1,000 patient days (range 0.1 to 3.15), followed by medicine (range 0.09 to 2.03). One psychiatry unit reported only preventable adverse drug events (no potential adverse drug events).

Discussion

Reporting adverse drug events serves as an aid in learning from experience. Our comparisons with literature^{3, 5, 7, 16, 17} indicated much lower reporting of preventable adverse drug events and somewhat better, but still considerably low reporting of potential adverse drug events into the voluntary RMEES. These results are similar to other studies involving voluntary incident reporting.^{34, 35, 37–39, 43} The extent of reporting was much better with PHRED (mainly for potential adverse drug events) in comparison to RMEES. Nevertheless, there was wide variation in reporting patterns among the various service areas, and among the individual hospital units comprising each service in both systems.

Studies of hospitalized patients suggest that adverse drug events are common, although the reported rates have varied depending on the criteria used for defining the events and the mode and intensity in which they were sought.^{3, 4, 10, 39, 44–47} Bates et al. found that 1 in 100 medication errors resulted in an adverse drug event.¹⁶ Another report indicated that preventable adverse drug events occur in up to 4 percent of hospitalized patients.⁴⁸ Although the true universe of adverse drug events is unknown, extrapolating this to our study we could expect approximately 3,770 preventable adverse drug events (4 percent of 94,445 admissions) during the 22-month time period. However, only preventable adverse drug events were actually reported, which is consistent with other studies that suggest that self-reporting typically identifies only about 5 percent of actual events.³ In fact, this problem of significant underreporting with voluntary incident reporting is well documented in the literature.^{34, 35, 38, 39} Our study also suggests that in addition to generally poor reporting levels, there is considerable variation in the extent of reporting among various nursing units and services, implying the need for standardized training on adverse drug event reporting.

Although the extent of reporting of total adverse drug events in PHRED was higher than in RMEES, the wide variation in reporting among the individual nursing units and services also supports the notion that to a large extent, voluntary reporting is driven by individual attitudes and behaviors, which in turn are influenced by a complex combination of factors, including reporters' perceptions of the severity and extent of risk that the event poses, reporting culture at the institution, fear of punishment, and liability concerns.⁴⁹ Equally compelling is the notion that reporting could reflect the culture on a particular nursing unit. A study of the effects of group- and organizational-level factors on administering drugs to hospitalized patients in different patient care groups suggested that differences in unit properties were associated with differences in error rates.⁵⁰ This study suggested that shared perceptions about the consequences of making a mistake within a unit, influenced by leadership behavior, may influence willingness to report mistakes. We noted a modest relationship between the potential and preventable adverse drug event rates among the various services for RMEES reported events, suggesting that nursing units that report numerous potential adverse drug events do not necessarily report many preventable adverse drug events. This further supports the importance of local unit culture and individual attitudes in determining reporting behaviors.

PHRED is a reporting system focused only on medications. Such narrow reporting systems may result in higher levels of reporting than traditional incident reporting as they match the professional expertise to the problems being examined and promote rapid and effective analyses.¹⁹ However, even with PHRED, there was minimal reporting of preventable adverse drug events.

There are several limitations to this study. This analysis depended heavily on the event details provided in the RMEES database, some of which were ambiguous; further evaluation of event types and reasons could not be performed due to lack of access to charts and to persons reporting the incidents. This also precluded our ability to classify the severity level of preventable adverse drug events. Nevertheless, we anticipate that most of the preventable adverse drug events reported in RMEES would be in the significant to serious range, with sentinel event reports being completed for the more serious fatal and life-threatening events. Also, since our study involved only self-reports from RMEES and PHRED, we were unable to make comparisons of the level of incident reporting with more objective measures such as chart reviews, or computerized adverse event detection methods, which would have inherently been better comparison measures.

Incident reporting has played a beneficial role in other high-risk industries such as aviation,⁵¹ and despite its limitations, it will continue to be an important and relatively inexpensive means of capturing data on errors and adverse events. However, because incident reporting does not capture the true rates of adverse drug events, health care organizations should be cautious in their interpretation of event rates or counts obtained from incident reporting systems and should avoid using them to produce quantitative estimates of harm for quality assessment or comparison purposes. On the other hand, incident reporting provides rich qualitative data concerning the types and patterns of events. Because frontline practitioners most familiar with the event typically generate incident reports, these systems provide unique and valuable information on system-based causes of events, thus facilitating systemwide quality improvement and patient safety.

Incident reporting also generates new knowledge of events that may have never occurred before. The potential adverse drug events, which are reported more frequently, may suggest a trend that could help in identifying processes that have the potential for serious harm. We believe that voluntary incident reporting will assume greater importance as the use of information technology in health care increases with the widespread introduction of bar coding and computerized prescriber order entry systems. These safeguards will lead to further decreases in the frequency of commonly occurring and more easily recognizable adverse drug events. Consequently, the ability of incident reporting to uncover unique occurrences will assume greater relative importance. Also, de-identified information of rare events obtained from incident reporting can be collated with similar reports from other institutions, thereby increasing the analytic power for detection of rare events.

Conclusion

Our analysis shows the variability in adverse drug event reporting across nursing units and across systems at different points in the medication delivery process. Perhaps hospitals should provide standardized education to all frontline staff in order to minimize the variation in error reporting. Reporting systems that focus on certain types of events and that are aligned with reporters' expertise may yield increased reporting. We anticipate that with greater use of information technology, the utility of voluntary reporting systems may improve, but voluntary systems cannot be relied upon for quantitative determination of error rates or harm. Future studies should examine the barriers to reporting, and evaluate various strategies to enhance reporting.

Acknowledgments

Support for this work came from Grant # U18 HS1189801 from the Agency for Healthcare Research and Quality.

Author affiliations

Department of Medicine, Washington University School of Medicine (RD, MK, WCD, TB, VF). BJC HealthCare, St. Louis, MO (WCD, EC, TB, and VF).

Address correspondence to: Melissa J. Krauss, M.P.H.; Division of Infectious Diseases, Washington University School of Medicine; Campus Box 8051, 660 S. Euclid Avenue, St. Louis, MO 63110. Phone: 314-454-8570; e-mail: mkrauss@im.wustl.edu.

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