Appreciate your comments, and got me to thinking a bit more about a topic I really love, because ER docs are the ultimate probability workers, seeing a steady stream of almost undifferentiated patients (septic shock, then vaginal bleed, then persistent cough, then opioid user w a new pain). Sometimes we are so ignorant that the “prior probability” of a given disease is exactly 0.5, but mostly we have a vague idea (“we never see dz X here”). This is indeed an anchor, but it is not based on a covariate vector, or if so, then a very primitive one. A simple rule that most students find completely intuitive is the mnemonic: SNOUT (sensitivity rules out), important when your main job is “not missing a serious case”, like pulmonary embolus. And the obverse is SPIN “Specificity rule in”, also useful in ER when you can “rule in” a trivial self-limited illness like shingles. Even the LRP and LRN may not be worth the additional trouble of looking up or calculating the ratio, and the diagnostic odds ratio is definitely a bridge too far, because it is even harder to interpret, and is only a measure of discrimination rather than calibration. I don’t think clinicians are fooled into taking “spin” and “snout” too seriously. The rule is truly a “heuristic” to be used when you don’t have time to look something up or consult a validated model, i.e. not a formal procedure. The good news is that ER docs as a group more and more consult formal models on-line, on the wonderful website “MDCalc”.