Question

As defined by the IOM report, what is the difference between medical error, an adverse event, and diagnostic, therapeutic and preventive errors?

Answer 1

The IOM report enumerates and expands the categorization of the types of medical errors. These categories are diagnostic, therapeutic, preventive or related to therapeutic failures.

Clinical Errors

Definition and Patterns of Error

In the IOM report ‘To Err Is Human: Building a Safer Health System' , clinical error was defined as ‘the failure of a planned action to be completed as intended or the use of a wrong plan to achieve an aim'. In other words, errors can arise in planning actions or in executing them. The report listed adverse drug events (ADEs) and improper transfusions, surgical injuries and wrong-site surgery, suicides, restraint-related injuries or death, falls, burns, pressure ulcers and mistaken patient identities as examples of clinical errors. It commented that high error rates with serious consequences are most likely to occur in intensive care units, operating rooms and emergency departments.

It is widely accepted that medication error is the most common and preventable cause of patient injury. This includes the giving of the wrong drug or dose, by the wrong route of administration, to the wrong patient or at a wrong time. There is evidence that in acute hospitals the incidence of ADEs is 6.5/100 admissions and that 1% of these are fatal, 12% are life-threatening and 28% are preventable. Furthermore, it is estimated that there are 5.3 medication errors/100 prescriptions. These include missing dose (53%), dose errors (15%), frequency errors (8%) and route errors (5%), but only 1% of them were associated with ADEs. A considerable proportion (21%) of medication errors went undetected by pharmacists during the dispensing process and 23.5% of the undetected errors were likely to cause ADEs. The majority of overlooked errors were incorrect medication, incorrect strength and incorrect dosage .It is notable that errors occurring during the peri-discharge period in hospitalized patients and those following discharge were most easily missed . It is also estimated that the additional annual cost of ADEs in hospitalized patients in a 700-bed teaching hospital is USD 5.6 million . More recently, the additional cost of ADEs in community hospitals has been estimated as USD 3,000 per patient on average and an increase in length of stay of 3.1 days, similar to that found for academic institutions. In the elderly, ADEs added USD 65,631 to the cost per 1,000 elderly people managed within an ambulatory setting. Perhaps more importantly, many of the injuries caused by medical errors were due to substandard care and many were also preventable.

Drug Error Settings

The rates of medication errors in pediatric settings appear to be up to three times the rates in adult settings and are reported to be 5.7% resulting in 0.24% of ADEs . There are also comparable medication errors in ambulatory pediatric settings where the majority of preventable errors were due to parental drug administration.The rates in intensive care units do not appear to be different from those in other hospitalized patients, once the number of ordered and administered drugs had been controlled for. The rates in psychiatric hospitals are similar to those in other settings. In nursing homes for the elderly, there were 1.89/100 resident-months of ADEs and 0.65/100 resident-months of potential ADEs . In this population, of the ADEs, 6% were life-threatening and 38% were serious. In total, 51% of the ADEs were judged to be preventable. ADEs in nursing homes commonly involved the use of psychotropic agents resulting in neuropsychiatric side effects, falls and oversedation. In ambulatory elderly people, the rate of ADEs was 50.1/1,000 person-years. Many of these ADEs were serious, life-threatening or fatal (38%) and it was judged that 42% were preventable. The most commonly implicated drugs were cardiovascular agents, diuretics, nonopioid analgesics, hypoglycemic drugs and anticoagulants. The risk of ADEs was markedly elevated in elderly patients who had multiple conditions, were receiving multiple drugs including nonopioid analgesics, anticoagulants, diuretics and anticonvulsants. ADEs in ambulatory settings such as primary care are common and also occur in ambulatory adult and pediatric chemotherapy settings.

A systematic review of 22 studies involving 3,755 patients found that errors in prescription medication histories occurred in up to 67% of cases and these included commission errors as well as omissions, incorrect dose and incorrect frequency. For example, a patient who was admitted in a coma had her medication brought in by relatives including propafenone that had been discontinued months before.

In summary, prescription errors associated with drug errors and ADEs were frequent in practically all health-care settings. However, it is difficult to make ready comparisons because rates are reported differently across studies. Some studies report rates per 100 admissions, others report rates per 100 resident months, whilst others report rates per 1,000 person-years. This is a fundamental problem that needs to be resolved.

Nondrug Events

In addition to ADEs, other adverse events in hospitalized patients include wound infections and technical complications. It is estimated that nearly half of all adverse events in hospitals are associated with surgical operations. Those adverse events not associated with surgery included diagnostic mishaps, therapeutic mishaps (errors of omission) and events occurring in accident and emergency departments . Diagnostic errors rather than technical mishaps or adverse consequences of medication errors are also relatively common. For example, delay or diagnostic errors in cervical spine injuries occurred in approximately 4% of cases; this points to the need for the appropriate use of a standard 3-view cervical spine series with careful interpretation of the images.