The next morning, her chest X-ray was normal, her lungs were clear on examination and she looked very well with normal vital signs. There was only one thing - he oxygen saturations were 92% on air.
A d-dimer was done to exclude pulmonary embolism (this was a low probability patient) - the result was exactly on the upper limit of normal. Everyone scratched their heads. A V/Q scan was requested and showed multiple pulmonary emboli.
"Something doesn't fit" is an important clinical tool - but usually requires experience to recognise. It is intuition ("unease") - or Type 1 thinking - which should force us to stop and analyse things more deliberately. However, even after deliberate analysis a modified Wells score and a d-dimer were "lying" in this case ... but intuition won out. What is even more interesting is we only know about cases we get right, not necessarily the ones we get wrong!