We found that approximately one in four prescriptions written by community-based providers in two states had at least one error, even without counting illegibility errors. Illegibility errors occurred on average more than once per prescription. The use of an e-prescribing system has the potential to reduce error rates markedly. E-prescribing systems linked with advanced CDS may have an even bigger impact, especially on errors with higher potential for harm.
Our study is one of only a few to characterize prescribing errors in ambulatory care settings and we are not aware of other multistate studies that have been performed. In comparing the providers from New York and Massachusetts, there was no significant difference in prescribing error rates for non-illegibility errors. Our observed rate of errors seems generally similar to that of other studies, although methodologies vary between studies and rates may differ between academic and community settings.3
For example, despite the use of the same methodology and pharmacist reviewer, the percentage of hand-written prescriptions containing at least one error in a study of four academic-affiliated primary care clinics in Boston was 11% compared with our rate of 27.8%.3
Community-based providers may have different prescribing patterns and fewer support systems than academic-affiliated providers, leading to higher error rates.
Although the majority of errors we detected were unlikely to result in serious patient harm, some might. Furthermore, even the less serious errors are important to study for their potential impact on efficiency as well as patient safety. Illegible prescriptions or those with missing information can lead to pharmacy filling errors or callbacks for clarification. Substantial time may be wasted for patients, prescribers, and pharmacists given the high frequency with which prescribing errors appear to occur. Callbacks probably also have important clinical implications. For example, a study evaluating pharmacy callbacks to 22 primary care practices to clarify prescriptions found that callbacks were common and problems for ‘acute’ medications, defined as medications in which administration delays could lead to worsening of a medical condition or cause prolonged pain, were not resolved on the same day 34% of the time.21
In addition, although our methods were not designed to capture near misses or preventable ADE, we still detected a near miss rate of 1.5 per 100 prescriptions and there were likely to be additional near misses and preventable ADE that occurred but were not detected. A previous study showed that 4% of ambulatory patients with prescription errors experienced a preventable ADE.3
Further studies should be conducted in the community setting with methods specifically suited to detecting near misses and preventable ADE.
Understanding the epidemiology of prescribing errors in the outpatient setting can inform strategies for reducing their frequency and severity. This includes the use of e-prescribing, which has significant potential for improving patient safety.7
We found an overall rate of 175.1 illegibility errors per 100 prescriptions, all of which would be eliminated by even the most basic e-prescribing system. However, advanced CDS appears important to achieve even greater safety gains.
By characterizing ambulatory prescribing errors, CDS can be designed so that it targets the most frequent types of errors. For example, the two most common types of errors we found that were judged to be preventable with advanced CDS were inappropriate abbreviation errors and direction errors. CDS that automatically converted inappropriate abbreviations into acceptable abbreviations would eliminate this type of error. Pre-populated direction fields with clear and complete instructions for certain drugs might eliminate many direction errors. Future studies should be conducted to determine the actual impact of various e-prescribing systems with CDS on ambulatory prescribing errors, as few such studies have been conducted.3
This is particularly important given the expected increase in use of e-prescribing as a result of the federal stimulus package and meaningful use criteria.13
Our study has several limitations. We had only one reviewer for each prescription, although joint review of a subset of prescriptions revealed excellent agreement. This may account for differences in rates of prescribing errors between the New York and Massachusetts providers when illegibility errors were included, as ultimately the determination of legibility is subjective. We focused on prescribing errors and were limited by our methods to comment on near misses and ADE. In addition, the providers in our study were not blinded to the study's purpose. Our error rates might, therefore, be underestimates if physicians attempted to be particularly careful while writing prescriptions during the study period. The practices that elected to participate might not be representative of all practices, and might have lower rates than practices at large.