Transcript Slide 1
Clinical Reasoning Skills STEPP Course ST1;2011 Peter Macfarlane • intellectual process; leading to a ‘working diagnosis’ & management- discussion • some puzzles • sound medical principle;.. ‘diagnosis precedes treatment’.. • ...right diagnosis...right treatment • ...no diagnosis/wrong diagnosis;..! • APLS/emergency approach vs • classical history/examination/formulation/?Ix/progress • Hx /Ex ...the medical student approach, exhaustive data..but no idea what it means!) • then; hypothesis/analytical/deductive approach • mental shortcuts (heuristics) • then iterative diagnosis approach...’I know what’s going on here; ...series of closed questions to check this.... • pattern recognition; ‘ducks’ quick: like recognizing a friend slower: patterns/clusters • Stepwise ‘rule outs’; used to exclude ‘don’t miss’ diagnoses • probabilistic reasoning; ‘zebras’ ‘informal’; e.g. -age -duration illness -’red flags’ • ‘formal’ probabilistic reasoning the Bayesian approach • • • • • Sensitivity Specificity Positive predictive value Negative predictive value know the 2X2 table • SpP IN : • SnN OUT : • SpP IN : test(or Sx/Sg) with high Specificity performance, Positive result is a good ‘rule IN’ • SnN OUT : test (or Sx/Sg) with high Sensitivity performance, Negative result is a good ‘rule OUT’ • # • investigations...beware of pitfalls. -’paralysis by analysis’ - treat the child not the numbers -always question whether you know what the test result means (values,pos,neg), before you start. -’sometimes the best thing to do for the patient (child) is to spare them the misery of a useless intervention’ • keep it simple; Occam’s Razor (1 diagnosis), but learn how to juggle complex multiple problems.. • Test of treatment • Test of time, beware pressure to act.... • ‘don’t just do something, stand there!’ • if no diagnosis- keep an open mind, think aloud and get advice (foster ethos of 2nd opinion) • abandon the ‘diagnosis’ when things don’t go to plan • When the diagnosis is ‘obvious’ ; avoid premature closure; always ask ‘what else could this be?’ ..........think beyond the obvious; avoid the cognitive trap • recognize your own biases • # Test of Treatment • ‘first do no harm’, Test of Treatment rarely leads to robust diagnosis; nearly always better to use ‘test of time’ (except in critical illness). • lots of confounders.... ‘treatment’ trial apparent effect TP FP uncertain ? no apparent effect or worse TN FN trial of treatment confounders • False positives • placebo • spontaneous improvement/remission • natural fluctuation in disease process • False negatives • side effects • wrong drug/dose/duration • natural fluctuation in disease process • drug resistant disease variant ways to improve test of treatment • establish the baseline • agree the end point • objective measurement if possible; if not reduce ‘subjectivity’ • keep everything else the same • careful thought about drug selection, dose route, duration • Use the ‘3 step protocol’; multiple trials of n=1 • # • Questions?