Strengths and limitations
The 15 general practices included in the study were reasonably representative of English general practices in terms of list size, number of GPs per practice, age profile, and points achieved in the Quality and Outcomes Framework, although they were more deprived. The sampling strategy enabled GP training practices and dispensing practices to be included. Compared with overall figures for England, the practices were more deprived.
To avoid any problems with sampling bias at the practice level, a random sample of patients was obtained from each practice. However, it is possible that the recruited practices had relatively high levels of interest in prescribing compared with other practices, and a greater openness to external scrutiny of potential prescribing errors, which could have caused the study to underestimate the true rate of prescribing errors. The pharmacists who collected data for the study all had clinical experience and were provided with training in identifying errors. Nevertheless, it is possible that they varied in their ability to detect potential prescribing and monitoring errors. A validated approach to the definition of error was used in the study, and a multidisciplinary panel was used to decide whether an error was present or not. A consistent approach was also used throughout the study to the application of the error definitions used. Nevertheless, it is possible that a different panel would have come to different judgements, and this highlights one of the challenges of consistent application of error definitions across studies. The present study focused on errors associated with prescribing and blood test monitoring. With more resources, it would have been helpful to have investigated errors associated with other aspects of medicines management in primary care, as done recently in English care homes.6
The multivariable analysis undertaken allowed associations between the prevalence of prescribing and monitoring errors and a range of factors to be explored, while taking account of potential confounders. Statistical significance for all analyses was set at <0.05 (two-sided) and some may regard this as relatively weak. Nevertheless, many of the findings were highly statistically significant.
Comparison with existing literature
This study was larger than previous UK studies, and used robust methods and definitions. The error rates are in line with those reported previously,3–6 but the large and representative sample makes the estimates more precise. The most recent of previous studies found a prevalence of prescribing error of 8.3% and monitoring error of 14.7%,7 albeit it in residential and nursing home patients.7 In contrast, the prevalence of prescribing errors in UK hospitals was 8.9%,15 and in a US hospital was 6.2%.16 Internationally, prescribing errors affect a median of 7% (IQR = 2–14) of medication orders in hospitals.17
The prevalence of prescribing or monitoring errors was particularly high in certain groups of patients: older people, children, men, and those on multiple medications. The high prevalence in older people has been noted elsewhere,6 and is of particular concern because of greater susceptibility of older people to experiencing medication-related harm. The high prevalence in children highlights the need to ensure that correct doses are prescribed with clear dosage instructions, but despite concerns from another study, off-label and unlicensed prescribing was not found to be an important cause of error.18 The finding that patients taking multiple medications have increased risk of error (an association that went beyond the additive effect of each medicine) is of concern, especially as those taking 10 or more medicines had an almost 50% risk of an error during a 12-month period. These findings support those of other studies,19 and highlight the need to find more effective ways of managing polypharmacy.20 The lower risk of error in women is a surprising finding, and is in contrast to findings suggesting that women are at greater risk of adverse drug events.21 It is possible, however, that GPs are more cautious when prescribing for women, hence the lower risk of error.
Drugs associated with a higher risk of error included those requiring a monitoring test, musculoskeletal drugs (most commonly non-steroidal antiinflammatory drugs), and those used for malignant disease and immunosuppression (although the sample was small in this last group). This highlights the need for GPs to pay particular attention to correct prescribing and monitoring of medications associated with the highest risk of error (and associated adverse events). Some of the most serious errors related to the prescription of warfarin without access to blood-test monitoring (Box 2). Given the dangers associated with this drug, it is essential that prescribers have access to the latest international normalised ratio before prescribing, and adhere to local and national policies.22 In addition, this study identified two cases in which drugs were prescribed for patients with a computer-recorded allergy to the drug. Given the design of GP computer systems, it is almost certain that these prescribers would have overridden a hazard alert. Therefore, there is a need to make it more difficult for prescribers to override alerts for the most serious hazards.23
In addition to the points made above, there are several other approaches by which prescribing and monitoring errors could be reduced in general practices, based on the findings of this study. Given that the most common type of error detected in the study was ‘incomplete dosage instructions’, it is important for GPs to take the time needed to provide clear and complete instructions, particularly for high-risk medicines. To help with this, the latest GP computer systems are able to provide ‘order sentences’ (dosage instructions) that are appropriate for each medication prescribed. Greater use of this functionality by GPs could substantially reduce error rates. Given that monitoring errors are another common category of error, it is important for general practices to ensure that they have robust systems in place to make sure that essential blood-test monitoring is done. GP computer systems can help with identifying patients who need monitoring, and this can also be done at prescription reviews. These reviews can also act as an opportunity to identify and correct errors, but the present study showed that repeat prescriptions were no less likely to contain an error than acute prescriptions. This suggests that prescription reviews may not be as effective as they could be, especially in patients taking multiple medications, and in higher-risk complex patients. It may be helpful to consider different models for conducting these reviews. For example, involving pharmacists and geriatricians in the review of older patients on multiple medications may help reduce unnecessary polypharmacy,20 and also reduce errors.
Pharmacists can also help GPs to reduce prescribing errors by identifying patients at risk (based on searches of the GP computer system), and facilitating appropriate management of any problems identified.24 This approach, would be suitable for tackling some of the errors observed in this study, particularly monitoring errors. Overall, there is considerable scope for GP computer systems to help reduce many of the prescribing errors identified in this study. In addition to points made already, the most advanced systems can help provide advice on correct dosage, based upon a patient’s age, weight, and/or renal function. They can also provide alerts for contraindicated prescribing. A key challenge, however, is to avoid over-alerting prescribers, and to design systems to minimise the risk of accidentally overriding alerts for potentially fatal errors.
It should be noted that the study reported in this paper was part of a larger investigation funded by the General Medical Council (GMC) in the UK, and further details are available from the GMC website.25
Implications for future research
Further research is now needed to develop and test interventions to reduce the prevalence of prescribing and monitoring errors in general practices. It is already known that computerised clinical decision support can help reduce prescribing errors in hospitals,26 but there is a need for more studies in primary care, particularly to evaluate the more sophisticated systems in current use and to determine whether there are safety benefits to reducing the hazard-alert burden on prescribers. Further research is also needed into whether the prevalence of prescribing and monitoring errors in general practice can be reduced by education, training, audit, and practical support, as demonstrated previously.24 It is also important to evaluate the effectiveness of systems-based approaches to reducing prescribing and monitoring errors whereby processes used in general practices such as repeat prescribing, medication review, and monitoring are optimised. Finally, it would be helpful to do further research to determine the extent to which the prevalence of prescribing and monitoring errors can be reduced by more extensive involvement of clinical pharmacists in promoting high-quality, safe prescribing in general practice. For example, a model could be developed in which pharmacists work with GPs to address the most important factors associated with error.
Prescribing or monitoring errors occurred in one in 20 prescription items, and most of these were judged to be of mild to moderate severity; one in 550 prescription items contained a severe error. The risks of error were higher in children, older people, male patients, and those on multiple medications. Several groups of drugs were associated with higher risks of error, including those requiring blood-test monitoring. Having identified the most common and important errors, and the factors associated with these, strategies to prevent future errors should be developed, based on the study findings.
