The Evidence Crisis: Causal Inference – Don ’ t be a chicken (Part 3)

By ANISH KOKA Part 1 Part 2 Physicians have been making up numbers longer than people have been guessing weights at carnivals.  How much does this statin lower the chances of a heart attack? How long do I have to live if I don’t get the aortic valve surgery? In clinics across the land confident answers emerge from doctors in white coats.  Most of the answers are guesses based on whatever evidence about the matter exists applied to the patient sitting in the room.  The trouble is that the evidence base used to be the provenance of experts and anecdotes that have in the past concluded leeches were good for pneumonia. And so came the randomized control trial to separate doctors from homeopaths.  Random assignment seeks to achieve balance between two groups for everything but the treating variable to isolate the effect of the treatment.  But does randomization really guarantee a balance between groups?  At least the known confounders may be measured in the two groups, but what about unknown confounders? Consider some examples: Blood stream infections are currently treated by antibiotics targeted towards the specific organism found in the blood.  The distribution of organisms within the blood stream is as follows: Vancomycin is active against S.aureus, Coag Negative Staph (CoNS), and other gram (+) organisms.  Cefepime is active against Gram negatives.  Now imagine a world where there was no understanding of the different organisms that caused blood stream infecti...
Source: The Health Care Blog - Category: Consumer Health News Authors: Tags: Uncategorized Source Type: blogs