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Background. First impressions are thought to exert a disproportionate influence on subsequent judgments; however, their role in medical diagnosis has not been
systematically studied. We aimed to elicit and measure
the association between first impressions and subsequent
diagnoses in common presentations with subtle indications of cancer. Methods. Ninety UK family physicians
conducted interactive simulated consultations online,
while on the phone with a researcher. They saw 6 patient
cases, 3 of which could be cancers. Each cancer case
included 2 consultations, whereby each patient consulted
again with nonimproving and some new symptoms. After
reading an introduction (patient description and presenting problem), physicians could request more information,
which the researcher displayed online. In 2 of the possible
cancers, physicians thought aloud. Two raters coded independently the physicians' first utterances (after reading
the introduction but before requesting more information)
as either acknowledging the possibility of cancer or not.
We measured the association of these first impressions
with the final diagnoses and management decisions. Results. The raters coded 297 verbalizations with high interrater agreement (Kappa = 0.89). When the possibility of
cancer was initially verbalized, the odds of subsequently
diagnosing it were on average 5 times higher (odds ratio
4.90 [95% Cl 2.72 to 8.84], P < 0.001), while the odds of
appropriate referral doubled (OR 1.98 [1.10 to 3.57], P =
0.002). The number of cancer-related questions physicians
asked mediated the relationship between first impressions
and subsequent diagnosis, explaining 29% of the total
effect. Conclusion. We measured a strong association
between family physicians' first diagnostic impressions
and subsequent diagnoses and decisions. We suggest
that interventions to influence and support the diagnostic
process should target its early stage of hypothesis generation. Key words; family medicine; provider decision making; cognitive psychology; heuristics and biases. (Med
Decis Making 2017;37:9-16)
