ADEs: Looking for predictability in a panoply of circumstances
ADEs: Looking for predictability in a panoply of circumstances
Adverse drug events increase costs and consequences
In research looking at variables that could contribute to an increased risk of sustaining an adverse drug event (ADE) certain age groups, diagnoses, admission sources, types of insurance, and use of specific medications or medication classes were all associated with increased adverse event rates at a medical center.
"Although each adverse event may have arisen from a unique combination of circumstances, we found a measure of predictability in patterns of adverse events," says Philip Johnston, Pharm.D., assistant director of pharmaceutical services at Vanderbilt University Medical Center in Nashville. "Future efforts should include drugs specifically involved in adverse events, as well as separate analyses of medication errors and adverse drug reactions.
Johnson tells Drug Formulary Review his analysis of adverse drug events started as part of routine quality improvement measures at the medical center. He tells us there was interest in more than routine reporting and a desire to look for ways to predict who might be likely to sustain an adverse event.
As many as 1.3 million accidental patient injuries are caused each year by medical treatments, with mistakes occurring in 19% of all medication doses given in hospitals, usually during drug administration. Johnston notes that patient safety in hospitals has come under intense scrutiny in both the public and private sectors. An American Society of Health-System Pharmacists May 2002 survey found that 85% of respondents expressed concerns about at least one medication-related issue such as receiving interacting medications, having harmful adverse effects from a medication, or receiving the wrong medication. With an estimated cost of $2,000 per adverse drug event, institutions should not ignore this problem, Johnston says.
Although some published literature has isolated some variables associated with increased risk of adverse drug events, no study has definitively specified a model that predicts ADEs. Johnston says controversy exists about predictive modeling of ADEs. Early work to develop an ADE predictive model yielded discouraging results.
Authors of that early study decided that ADEs could not be predicted by observing the patient characteristics and hospital environment factors used in their study. But there were design flaws found in the study and other researchers identified common and repeated patterns of preventable ADEs.
Johnston says the purposes of his study were to (1) identify specific patient and clinical characteristics associated with an increased risk of sustaining an adverse drug reaction or medication error, collectively termed adverse events and (2) identify factors or medication-use process steps requiring further investigation.1
Professionals expected to report ADEs
During the study period, reporting of adverse events was an expected professional activity. The medical center has developed methods of reporting adverse events including secure e-mail, telephone reporting, paper reports, and secure reporting through the CPOE (computerized physician order entry) system. Education by the pharmacy and risk management departments has centered on penalty-free reporting. Severity of adverse events was determined by the pharmacist who evaluated each event that was reported.
The study population included all patients admitted to the medical center hospital between January 1, 2000, and June 30, 2002. The initial data for adverse events consisted of adverse event reports maintained by the pharmacy. Some 84,021 admissions occurred during the study period. After removing 23,708 duplicate admissions from the control group, 59,531 were retained in that group for the analysis. A total of 782 adverse events were reported and included a combination of 83 adverse drug reactions and 699 medication errors. Medication errors that did not cause patient harm and process errors that did not involve patients were removed from the database, leaving 675 patients with adverse events to be included in the analysis.
Analysis showed adverse events occurred in a higher percentage of patients who were less than one year old or at least 60 years old. A higher percentage of adverse events were reported in men than in women, but the groups were not significantly different when comparing those with an adverse event and those without an adverse event. Among the various races of patients involved, the highest percentages of adverse events were reported for whites and blacks. No significance among races was found between the adverse event and non-adverse event groups.
Evaluation of admission sources showed that a doctor's office, clinical referrals, and local hospital transfers accounted for higher rates of adverse events than other sources and that patients experiencing an adverse event were more likely admitted from those sites. There were significant differences between the control and adverse event groups in the third party, Medicaid, and Medicare patients.
Problems found in nine diagnostic groups
Nine diagnostic groupings evaluated were significantly different between the adverse event and control groups — respiratory failure; multiple myeloma; blood disorders; disorders of fluid, electrolytes, or acids-bases; respiratory distress syndrome; myeloid leukemia; pneumonia; congestive heart failure; and aplastic anemia. Medication groupings associated with a large number of adverse events included antineoplastics and blood formation and coagulation agents.
Johnston says that when the findings from the training set were compared with the validation set, age, high-risk admission sources, and high-risk insurance class were found to be important risk factors for an adverse event.
According to Johnston, previously published case reports of ADEs have identified several potential factors associated with a high rate of ADEs, including female sex, age 40 to 69 years, renal or liver dysfunction, and use of orally administered medications. In many studies, he says, the age group identified to be at highest risk of an adverse event are those 15 to 60 years old, reflecting the number of patients in the study, the increased number of patients in that age group who experience trauma or surgery, and the increased rate of disease onset during those years. However, he says, the Vanderbilt data showed a very different pattern, with the very young and the older patient populations demonstrating an increased risk of adverse events.
Also, relatively healthy and moderately ill patients tended to exhibit a higher risk of sustaining a significant adverse event than did sicker patients. The drugs most commonly implicated in adverse events in other studies were central nervous system agents, antimicrobials, antineoplastics, and cardiovascular agents, as well as those requiring therapeutic monitoring. In other studies, also, adverse events were reported to occur more commonly in intensive care units than in general care units, but this was not evaluated in the Vanderbilt study.
Johnston tells Drug Formulary Review that researchers were surprised not to find a greater association between adverse events and newer drugs, pediatrics, and oncology. "We have a hunch that people report what they know other people will accept," he says. "It's safe to report something like morphine with respiratory distress. But if they report something new, they need to take the time to explain and that might make them less likely to do so."
Three-year follow-up on tap
Using the key indicators and factors associated with adverse events gleaned from the study, Johnson and colleagues will conduct a detailed analysis of adverse events occurring in congestive heart failure patients at Vanderbilt. "Over three years, an education effort will be launched for health care practitioners, advising them of the factors associated with adverse events in this group and soliciting their assistance to verify these indicators and develop actions to avoid them. Multiple measures will then be implemented to prevent adverse events associated with these indicators. Finally, these indicators will be analyzed retrospectively to determine what effect our efforts have had."
Johnston says researchers still don't think they have good baseline information against which comparisons can be made. He says steps must be taken to make it easier to report adverse events, including have terminals next to each patient. "We need to know what happens before and after and not just a snapshot," he says.
According to Johnston, improving the rate of adverse events requires that it become a high priority at the institution, something he says Vanderbilt is doing. "Part of the program is to identify things that we have to work on to get better," he says. "We're undertaking a three-year improvement program."
[Editor's note: Contact Dr. Johnston at (615) 322-0712 or e-mail [email protected].]
Reference
- Johnston, Philip E. et al., Assessment of Drug Events Among Patients in a Tertiary Care Medical Center, American Journal of Health-System Pharmacists, 2006;63(22):2218-2227.
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