Human Errors in Medicine

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Human Errors in Medicine

• Lecture Notes for HI6301 - Week 12
• Jiajie Zhang
• March 29, 1999

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The Extent of Human Errors
From Van Cott, 1994
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The Extent of Human Errors in Medicine

• Human errors in healthcare are rarely
  catastrophic. But

• Human Error Avoidable mistakes kill 100,000
  patients a year. (Washington Post, February 18,
  1992)

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Human Errors in Hospitalization (Brennan et al.,
1991)
3.7 adverse events
30,121 Records 51 Hospitals
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Types of Human Errors in Medicine

• Administration of Medications
• Giving medication to the wrong patient or to the
  right patient in an incorrect dosage or at the
  wrong time.
• Factors
• Excessive nursing or pharmacy staff workload
• poor labeling, poor lighting
• illegible prescriptions
• improper storage
• inventory and control procedures

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Types of Human Errors in Medicine

• Image Interpretation
• Diagnostic errors
• Sonograms
• X-ray
• CAT scan
• Electrocardiograms
• etc.

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Types of Human Errors in Medicine

• Medical Technology Use
• 50 alleged failures of devices are due to human
  errors (Nobel, 1991).
• Many factors
• Devices are not standardized
• Does not follow human factors principles
• Does not match users mental models
• Incomplete and difficult to comprehend operating
  and maintaining procedures
• Inadequate training or supervised practice

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Types of Human Errors in Medicine

• Laboratory Testing
• Testing errors in 66 of the laboratories that
  offered drug-screening services in New York
  State. (Van Cott, 1994).
• 262.6 milligrams/liter cholesterol was tested in
  in 5000 top laboratories in the nation. The
  reported values were 101-524 mg/liter.

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Types of Human Errors in Medicine

• Radiotherapy
• 50 millicuries (incorrect) rather than 3
  millicuries (correct)
• A wrong patient was administered 100 rad to the
  brain

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Types of Human Errors in Medicine

• Patient Billing
• Errors in 97 of a sample of 13,000 audited
  hospital bills (Merken, 1989)
• 38,000 for ulcer surgery

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Types of Human Errors in Medicine

• Other types
• Errors in patient care caused by illegible
  handwriting.
• Errors in anesthesia
• Mismatching of blood types

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Statistical Errors in Clinical Practice

• Availability Bias
• Caused by ease of access of information
• Examples
• ----n- (125 words), ---ing (880 words)
• k____, --k___ (which one has more words?)
• Rare and exotic diseases are overrepresented in
  medical journals, leading to overestimation of
  their probability

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Statistical Errors in Clinical Practice

• Conjunction fallacy
• Given that a 55-year-old woman had a pulmonary
  embolism, which of the following is more likely?
• The woman had hemiparesis and dyspnea
• The woman had hemiparesis

• 91 internists selected the first answer.

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Statistical Errors in Clinical Practice

• Anchoring Bias
• Initial estimate affects later judgment
• Example
• 12345678

512

• 87654321

2250

• The correct answer is 40320

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Statistical Errors in Clinical Practice

• Causal Schemas
• Apply causal relation to correlation
• Example
• Predict daughters eye color from mothers eye
  color

• Predict mothers eye color from daughters eye
  color

• Answer equally accurate

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Statistical Errors in Clinical Practice

• Hindsight Bias
• Think after the fact that they would have known
  something before the fact when in actuality they
  would not have.

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Statistical Errors in Clinical Practice

• Overconfidence
• More confident in judgments than is objectively
  justifiable.

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Statistical Errors in Clinical Practice

• Base Rate Neglect
• 71 of those with breast cancer were obese,
  54 of those without breast cancer were obese
• The probability of breast cancer in obese women
  is

or 71 - 54 17
71

• If 5 of the population have breast cancer, then
• The probability of breast cancer for obese women
  is
• 6 (71 (5/54)

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Statistical Errors in Clinical Practice
Bayes Theorem
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Statistical Errors in Clinical Practice
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Statistical Errors in Clinical Practice
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Statistical Errors in Clinical Practice