Factors That Can Lead to False Diagnoses

Physician-specific Problems
Insufficient History and Clinical Examination. A diagnostic
accuracy of 70% is reached through meticulous history-
taking and examination; misleading results are
rare ( 5%). Laboratory analyses and imaging studies
alone achieve a guarantee of only 30% and misleading
results occur in 10% of these cases. Insufficient history
and examination due to lack of time, lack of knowledge,
or lack of communication can therefore never be compensated
by further investigation.
Disregarding the Prevalence of Clinical Pictures. It is
dangerous to compare a present patient with a recent,
rare and interesting case from personal experience, perhaps
out of fear of not recognizing a rare disease.
“Common diseases are common, and rare diseases
are rare.” Our diagnostic efforts must therefore concentrate
primarily on the most probable diseases.
The simplest explanation is often the best one, and one
should try to assign the complaints and medical findings
of a patient to a single clinical picture. The situation
can be more complex in elderly patients.
Unavailable or Inadequate Knowledge. Current knowledge
can become obsolete or false within a few years.
Constant postgraduate training is required (case examination,
journals, books, continuing medical education,
internet).
Physician’s Characteristics. A physician needs an
enormous amount of self-criticism in order not to run
the risk of overestimation of his/her own capabilities.
Professional and personal contact among colleagues on
a regular basis (quality circle meeting) is essential.
Insufficient Judgement. This is an expression of inadequate
logical and structural procedures from the time of
medical findings to the diagnosis (logical thinking).
Failure to distinguish between medical findings and interpretation,
or unknowingly neglecting new results
which do not fit the diagnosis (preconceived notion), are
common mistakes.
A negative echocardiograph finding, for example,
must not lead to the rejection of a diagnosis of bacterial
endocarditis as suggested by a classic history and clinical
findings (according to the Duke criteria). This would
mean the omission of conclusive diagnostic procedures,
such as blood cultures, and empirical therapy possibilities.
Preexisting secondary diseases may obscure symptoms
of an otherwise classic diagnosis, e. g., angina pectoris
as the chief symptom of coronary heart disease is
frequently absent in a diabetic person.
Possible Errors of a Technical Nature. The great number
of available laboratory tests and technical examinations
means that it is necessary that the physician interpreting
the results in the clinical context be up to date on
their diagnostic significance.
Furthermore, the assumed prevalence of a disease is
always considered when assessing test results (pretest
probability). Whereas a slightly elevated serum alkaline
phosphatase level in a patient with lymphoma may indicate
liver involvement, the same value in a screened
asymptomatic patient is in all likelihood a false-positive.
Patient-specific Problems
Incorrect, Biased or Inaccurate Statements (made consciously
or unconsciously). These statements are based
upon forgetfulness, anxiety (e. g., fear of a serious disease
and the corresponding report from the doctor), or
fear of consequences in regard to official matters such as
suitability for military service, ability to drive a motor
vehicle, liability, etc. They may also occur in cases involving
addicts (alcohol, nicotine, analgesics, illicit
drugs), statements of sexual orientation, and consequences
pursuant to insurance laws. Another rare
phenomenon which can lead to false diagnosis is Münchausen
syndrome. The syndrome was named after the
tale of Baron von Münchausen. Such patients feign more
or less plausible, self-induced symptoms and repeatedly
present to physicians and hospitals to secure numerous
diagnostic tests and therapeutic interventions.
Preconceptions. These are conditioned from prior medical
findings and from reading popular medical journals.
They are frequently observed in patients with a smattering
of medical knowledge, and satisfy the need of
causality.
Inappropriate Behavior. This is characterized by a lack of
cooperation, excessive demands, and fear of disease.
Dissimulation for Various Reasons. There are many reasons
for this condition.
Masking of Symptoms and Findings of a Disease. Typical
examples of masking of symptoms are painless acute
abdomen in schizophrenic patients or in relation to
medications which are being taken, e. g., by drug addicts.