A string of mistakes: the importance of cascade analysis in describing, counting, and preventing medical errors

Abstract

Background: Notions about the most common errors in medicine currently rest on conjecture and weak epidemiologic evidence. We sought to determine whether cascade analysis is of value in clarifying the epidemiology and causes of errors and whether physician reports are sensitive to the impact of errors on patients.

Methods: Eighteen US family physicians participating in a 6-country international study filed 75 anonymous error reports. The narratives were examined to identify the chain of events and the predominant proximal errors. We tabulated the consequences to patients, both reported by physicians and inferred by investigators.

Results: A chain of errors was documented in 77% of incidents. Although 83% of the errors that ultimately occurred were mistakes in treatment or diagnosis, 2 of 3 were set in motion by errors in communication. Fully 80% of the errors that initiated cascades involved informational or personal miscommunication. Examples of informational miscommunication included communication breakdowns among colleagues and with patients (44%), misinformation in the medical record (21%), mishandling of patients' requests and messages (18%), inaccessible medical records (12%), and inadequate reminder systems (5%). When asked whether the patient was harmed, physicians answered affirmatively in 43% of cases in which their narratives described harms. Psychological and emotional effects accounted for 17% of physician-reported consequences but 69% of investigator-inferred consequences.

Conclusions: Cascade analysis of physicians' error reports is helpful in understanding the precipitant chain of events, but physicians provide incomplete information about how patients are affected. Miscommunication appears to play an important role in propagating diagnostic and treatment mistakes.

Figure 1.

Examples of cascade of errors revealed in physicians’ descriptions of incidents. Treatment (TR) = errors in administering treatments, medications, immunizations, and care plans; diagnosis (DX) = errors in screening, diagnostic examination and testing, and interpretation of findings; informational communication (IC) = errors in processing messages, instructions, and medical record data; personal communication (PC) = errors in interpersonal communication among providers and patients; CBC = complete blood count.

Figure 2.

Errors precipitating the 45 distal errors in treatment described in the narratives. Note: Errors in communication (shaded) predominate throughout the causal chain.

Figure 3.

Distribution across 5 domains of care for all errors (N = 184) reported in 75 incidents and for proximal (first or underlying) and distal (final or ultimate) errors at either end of the cascades (N = 83 and 84, respectively). Note: Distal errors predominantly involve treatment, but communication errors predominate at the outset. Treatment = errors in administering treatments, medications, immunizations, and care plans; diagnosis = errors in screening, diagnostic examination and testing, and interpretation of findings; informational communication (IC) = errors in processing messages, instructions, and medical record data; personal communication (PC) = errors in interpersonal communication among providers and patients.

Figure 4.

Consequences to patients as reported by physicians and inferred by investigators. Note: Physicians were more likely to report physical harms and less likely to report emotional or psychological effects.

Figure 5.

Analytic construct to incorporate Reason’s model of organizational accidents into the notion of cascades. Note: The construct recognizes that each error in the cascade can arise from error-producing conditions, which exist because of latent failures, and that the errors occur in the absence of adequate defenses (safeguards). The predisposing factors that contribute to each error are not necessarily distinct, eg, fatigue may cause error A and error B, nor does injury only occur as a result of distal errors.