Cases & Commentaries

Autopsy Revelation

Commentary By Kaveh G. Shojania, MD

The Case

A 45-year-old male with development delay
presented to the emergency department with acute abdominal pain.
His mother, who was his main caregiver, accompanied him. The mother
was talkative and answered all questions on his behalf, including
questions about his symptoms and past medical history.

The mother described the current episode as the
sudden onset of severe pain, which initially seemed to be in the
epigastric area, but had since moved over to the right upper
quadrant and flank. The patient nodded his assent throughout his
mother's account. Mother and son stated that the pain was no longer
as severe as it had been at its onset, roughly 2 hours earlier. She
stressed that he had experienced very similar complaints the
previous year, which were diagnosed as due to renal colic.

On physical examination, the patient was
moderately obese and appeared in mild discomfort, but no acute
distress. His vital signs were normal except for mild tachycardia
to 100 beats per minute. Abdominal examination revealed mild
tenderness with deep palpation in the epigastrium and right upper
quadrant. There was no costovertebral angle tenderness, and rectal
examination was unremarkable.

The emergency physician's working diagnosis was
renal colic, but he also considered the possibility of gallstones.
He planned to obtain a right upper quadrant ultrasound if the pain
did not respond to treatment for renal colic or if laboratory tests
suggested a hepatobiliary process.

The patient received an intramuscular injection
of ketorolac (Toradol), which provided significant relief, as did a
second injection 2 hours later. Serum chemistry and blood count
results returned within normal limits. Urinalysis was not
available, however, as the patient had forgotten the instructions
and flushed his urine sample. He was discharged with a prescription
for acetaminophen with codeine, instructions to drink at least 8
glasses of water a day, and a strainer for his urine in case he
passed a stone, all of which the mother stated she was familiar
with based on the previous episode.

The next morning, the patient's mother found him
in bed completely unresponsive and with no palpable pulse.
Ambulance personnel pronounced him dead at the scene. The medical
examiner requested an autopsy, which revealed a perforated gastric
ulcer and widespread peritonitis.

The Commentary

The discharge diagnosis of renal colic in this
case almost certainly reflected the operation of ascertainment bias
(seeing what one expects to find), anchoring (holding on to initial
impressions), "premature closure," and confirmation bias.(1-3) These last
two terms refer to the tendency to make up one's mind (prematurely)
about a diagnosis and then see all findings as consistent with that
diagnosis, even when such findings would be atypical (eg,
epigastric and right upper quadrant tenderness from kidney stones).
The importance of confirmation bias and other cognitive pitfalls
that affect diagnostic reasoning have been discussed in this forum
(see related commentary) and elsewhere, including our recent book
on medical mistakes.(1-5) A
different issue raised by this case, and one which has received
very little attention in the patient safety literature, concerns
the role of the autopsy as a tool for detecting important errors in
clinical diagnosis.

Despite its historical role in clarifying,
confirming or refuting clinical diagnoses, the autopsy has all but
vanished in many hospitals. In 1994, the last year for which United
States data exist, the autopsy rate for all non-forensic deaths had
dropped to below 6%, from rates of 40%-50% a generation
earlier.(6) A more
recent survey found that more than half of all hospitals in one
state reported performing no autopsies during a one-year
period.(7)

The marked decline in autopsy rates undoubtedly
reflects various factors, including reimbursement issues for
hospitals and pathologists, disappearance of the autopsy from
postgraduate educational criteria (except in pathology), the
dropping of minimum autopsy rates from regulatory guidelines, as
well as general unfamiliarity with autopsy and techniques for
requesting it, especially among physicians-in-training.(8) Perhaps the
most important reason, however, is that clinicians believe that
advances in medical technology have rendered the autopsy
unnecessary in all but extraordinary cases.

The assumption that major diagnostic errors have
become a rarity is not borne out by existing evidence. Numerous
studies document substantial rates of major diagnostic errors
detected at autopsy, including errors that likely affected outcome.
Studies comparing autopsy findings over 30-40 years at the same
institutions have generally found no change in the rates at which
autopsy reveals clinically important diagnoses that had escaped
antemortem detection.(9-11)
Clinicians often attribute these persistently significant and
unchanged rates of diagnostic errors to selection bias, arguing
that cases sent for autopsy are precisely those in which there is
diagnostic uncertainty.

My colleagues and I recently performed a
systematic review of the autopsy literature to examine time trends
in autopsy-detected diagnostic errors and address the impact of
case selection by clinicians.(12) We captured
the degree of clinical selection by considering the percentage of
decedents undergoing autopsy. In this model, an autopsy rate of
100% would represent no selection, while an autopsy rate
approaching zero would reflect extreme clinical selection. The
large number of studies available for analysis permitted generation
of a model of diagnostic error rates as a function of time, while
controlling for clinical selection, case-mix (medicine, surgery,
pediatrics, etc.), and country (US vs. Non-US).

Beginning in 1960, major errors—errors in
the principal underlying diagnosis or immediate cause of
death—decreased at a rate of 28.0% per decade (95% CI:
9.8-42.6%). Despite this relative decrease, the absolute rates of
major errors remain substantial. For instance, the estimates
generated by this analysis indicated that conducting autopsies in
all deaths occurring in a contemporary U.S. hospital would reveal
major diagnostic errors in at least 8% of cases, but possibly as
many as 22.8%.(12) Moreover,
diagnostic errors likely contributed to death in at least 3.8% of
all cases, but possibly as many as 7.9% of cases depending on the
percentage of decedents undergoing autopsy.

The modest impact of autopsy rates on diagnostic
error rates suggests that clinicians are overconfident in their
ability to select diagnostically unresolved cases for autopsy. This
interpretation is corroborated by prospective studies that found
clinicians to have little to no ability to predict cases likely to
yield "diagnostic surprises."(13,14) These
findings should themselves not come as a surprise. No matter how
advanced diagnostic technology may have become, the vast majority
of patients do not undergo 'gold standard' evaluations to establish
or confirm a working diagnosis.

In the current case, for instance, the patient
was discharged from the emergency department with a diagnosis based
almost entirely on the history and physical examination. This is
not inherently wrong; several studies have shown that some 70%-80%
of diagnoses are correctly made on history and physical
examination.(15-17) What
clinicians often lose sight of, however, is the frequency with
which diagnoses rest on little more than the clinical impression
and a few basic laboratory tests, rather than a definitive
biochemical, radiologic, or histopathologic result.

Of course, sophisticated tests do not guarantee
correct diagnoses, even when they have apparently provided a
definitive answer. For instance, one of the studies in the autopsy
literature specifically looked at cancer misdiagnoses in patients
who had undergone biopsy during life.(18) The
substantial discordance between antemortem and postmortem diagnoses
reflects a variety of factors related to the sensitivity and
specificity of diagnostic tests, but probably also reflects the
degree to which clinicians seize on a particular diagnosis among
the possibilities listed in radiology or pathology reports.

Clinicians are often annoyed at the litany of
conditions tacked onto cautiously worded interpretations from
radiologists and pathologists: "These findings are consistent with
X, but cannot rule out A, B, C, D and E. Clinical correlation is
advised." However, these differential diagnoses are given for a
reason, and sometimes, when one looks back to understand how a
pathologic or radiologic misdiagnosis might have occurred, one sees
that the clinicians did not continue to pursue a differential
diagnosis that was presented in a study report.(9)

Little is known about the root causes of
diagnostic errors, but any given case likely reflects the interplay
of human and system-related factors (Table).
Conversely, missed diagnoses detected at autopsy do not necessarily
represent errors. They may instead reflect acceptable limits of
antemortem diagnosis or atypical clinical presentations.
Nonetheless, clinicians have an intrinsic interest in important
missed diagnoses, even when they reflect atypical presentations or
shortcomings of current diagnostic approaches rather than quality
problems. Repeated detection of certain missed diagnoses may result
in the recognition that some patterns of presentation are more
typical than previously appreciated.

This case serves as a reminder of the persistent
need to remain vigilant for important misdiagnoses, and of the
value of the autopsy in bringing such cases to light. It also
illustrates the degree to which misdiagnoses continue to involve
common conditions, rather than "fascinomas" and "zebras."

Take-Home Points

  • Remain aware of the degree to which
    first impressions or a particular piece of information may have
    biased your diagnostic reasoning.
  • Avoid confirmation bias by having a very
    low threshold for reopening the differential diagnosis and playing
    "devil's advocate" with the working diagnosis.
  • Recognize the degree to which working
    clinical diagnoses are often based on limited information.
  • An autopsy is almost always reasonable
    to consider—do not confuse your (perhaps mistaken) impression
    of diagnostic certainty and the low value of an autopsy in finding
    a surprising diagnosis with your (perfectly natural) discomfort
    with asking the family for permission to obtain an autopsy.
  • Like discussing advanced directives,
    asking families about autopsy becomes much easier after you have
    received some guidance from a more experienced clinician and
    participated in a few such discussions.
  • For answers to common questions about
    autopsies, click here.

Kaveh G. Shojania,
MD
Department of Medicine
University of California, San Francisco

References

1. Croskerry P. Achieving quality in clinical
decision making: cognitive strategies and detection of bias. Acad
Emerg Med. 2002;9:1184-1204.[ go to PubMed ]

2. Croskerry P. The importance of cognitive
errors in diagnosis and strategies to minimize them. Acad Med.
2003;78:775-80.[ go to PubMed ]

3. Graber M, Gordon R, Franklin N. Reducing
diagnostic errors in medicine: what's the goal? Acad Med.
2002;77:981-92.[ go to PubMed ]

4. Kuhn GJ. Diagnostic errors. Acad Emerg Med.
2002;9:740-50.[ go to PubMed ]

5. Wachter RM, Shojania KG. Internal bleeding:
the truth behind America's terrifying epidemic of medical mistakes.
New York, NY: Rugged Land Publishing; 2004.

6. Burton EC, Nemetz PN. Medical error and
outcomes measures: where have all the autopsies gone? MedGenMed.
2000;2:E8.[ go to PubMed ]

7. Burton EC, Nemetz PN, Fisher WPJ, Newman WPI.
Institutional characteristics associated with hospital autopsy
performance: A survey of Louisiana hospitals [Abstract]. Am J Clin
Pathol. 2001;116:590.

8. Rosenbaum GE, Burns J, Johnson J, Mitchell C,
Robinson M, Truog RD. Autopsy consent practice at US teaching
hospitals: results of a national survey. Arch Intern Med.
2000;160:374-80.[ go to PubMed ]

9. Goldman L, Sayson R, Robbins S, Cohn LH,
Bettmann M, Weisberg M. The value of the autopsy in three medical
eras. N Engl J Med. 1983;308:1000-5.[ go to PubMed ]

10. Kirch W, Schafii C. Misdiagnosis at a
university hospital in 4 medical eras. Medicine (Baltimore).
1996;75:29-40.[ go to PubMed ]

11. Sonderegger-Iseli K, Burger S, Muntwyler J,
Salomon F. Diagnostic errors in three medical eras: a necropsy
study. Lancet. 2000;355:2027-31.[ go to PubMed ]

12. Shojania KG, Burton EC, McDonald KM, Goldman
L. Changes in rates of autopsy-detected diagnostic errors over
time: a systematic review. JAMA. 2003;289:2849-56.[ go to PubMed ]

13. Landefeld CS, Chren MM, Myers A, Geller R,
Robbins S, Goldman L. Diagnostic yield of the autopsy in a
university hospital and a community hospital. N Engl J Med.
1988;318:1249-54.[ go to PubMed ]

14. Cameron HM, McGoogan E. A prospective study
of 1152 hospital autopsies: II. Analysis of inaccuracies in
clinical diagnoses and their significance. J Pathol.
1981;133:285-300.[ go to PubMed ]

15. Roshan M, Rao AP. A study on relative
contributions of the history, physical examination and
investigations in making medical diagnosis. J Assoc Physicians
India. 2000;48:771-5.[ go to PubMed ]

16. Peterson MC, Holbrook JH, Von Hales D, Smith
NL, Staker LV. Contributions of the history, physical examination,
and laboratory investigation in making medical diagnoses. West J
Med. 1992;156:163-5.[ go to PubMed ]

17. Hampton JR, Harrison MJ, Mitchell JR,
Prichard JS, Seymour C. Relative contributions of history-taking,
physical examination, and laboratory investigation to diagnosis and
management of medical outpatients. Br Med J. 1975;2:486-9.[ go to PubMed ]

18. Burton EC, Troxclair DA, Newman WP, 3rd.
Autopsy diagnoses of malignant neoplasms: how often are clinical
diagnoses incorrect? JAMA. 1998;280:1245-8.[ go to PubMed ]

Table

Table. Example Root Causes of Diagnostic
Errors

Human Factors

System Factors

Faulty data gathering (eg, incomplete
history, cursory examination, inadequate laboratory tests)

Inability to perform needed tests in a
timely fashion

Failure to follow up on abnormal findings
(eg, the murmur that is never looked into or the high calcium that
no one follows up on)

Inability to access necessary medical
information (eg, outpatient records for hospitalized patients and
inpatient records for ambulatory patients)

"Premature closure"—Failure to
alter initial diagnosis when faced with inconsistent results

Poor communication between inpatient team
members (eg, different clinicians caring for the same patient
communicate their thoughts and plans solely through written chart
notes)

Failure to ask for assistance from a
consultant or supervisor when warranted

Poor communication between inpatient and
outpatient physicians