Reading the Medical Literature: Economic Evaluations.

Jul 12 2012 Published by under Uncategorized

Ok. I want to start off by saying that there must be something in the airducts here at the Scientopia underground lair/resort facility/staging area for the domination of the surface folk. And it isn't just the Genomic Repairman's most recent crime against nature and nature's god*. I'm come down with one of the many strains of biologic weaponry under development. I'm pretty sick and still on the downslope. I slept for like three and a half hours this afternoon, and I'm ready for bed again. So this is going to be a short post. I'm going to describe a few basic types of economic evaluation and then I'm going to take more alka seltzer cold and flu, which, to my knowledge, remains the only viable antidote to Drugmonkey's new hallucination powder, which is in the water here. I'm telling you, if this RSS feed is reaching the outside, send help! And Purina lemur chow!

So. Now that the housekeeping is out of the way, here's some stuff about economic evaluations, quickly, before the delirium sets in. In order for a study to be considered an economic analysis, two things must be compared. And the comparison must be made in terms of both outcomes, and costs. So, for example, two pills, with different costs, and different likelihoods for preventing an expensive adverse event like a stroke. Then, we can compare the costs of the intervention, and the costs associated with the adverse event at the rates we'd expect to find in the population based on adherence to a particular therapeutic regimen.

There are several types of cost studies, all similarly named and with small, subtle, and important differences. For example, a cost minimization analysis, which compares the costs of two or more equally effective interventions. A cost effectiveness analysis, which compares the cost and health consequences of two or more programs while expressing the the health consequences in a natural unit of cost per event, or cost per year of life. And a cost utility analysis, which is like cost effectiveness, but expressing the health consequence as a unit of time, rather than money, like Quality Adjusted Life Years (QALY).

A Quality Adjusted Life Year is a number between 0 and 1, where a 1 represents one year of perfect health, and 0 represents being dead. Sometimes there are negative QALYs, like when you're a victim of locked-in syndrome and being cared for by the people in "One Flew Over the Cuckoo's Nest".

Figure 1: Cost/Outcome Grid

So, what we'd love, in doing these analyses, is to find a bunch of interventions that go in the green field: lower cost, better outcomes. And we'll never accept anything in the red field, that being higher cost, worse outcomes. The yellow field we might occasionally accept, when it's a worse outcome, but a lower cost. If an intervention which costs almost nothing can replace an intervention that costs a huge amount, and have only a tiny bit worse outcome, that would be acceptable in a lot of cases. But most of the time, we live in the blue field, where we have to decide if a new, more expensive intervention justifies its higher cost with substantially better outcomes. According to class, the slop of that line is generally accepted to be, in the USA, at about $25K/QALY. This roughly corresponds to dialysis.

Cost-benefit analyses are often judged on two kinds of calculation schemes: the human capital scheme, where we measure the benefit of healthy contribution to the workforce, versus the cost of the intervention; and willingness to pay, where we measure what people say they would pay to avoid an adverse event, such as a stroke. Both of these have basic problems. In the former, people who don't contribute to the workforce are considered valueless. In the latter, people in difference circumstances will report vastly different values,and we can't be sure that if push came to shove, they'd actually do what they say, like pay $50K to not have a stroke, and plus that doesn't work anyway.

The big takeaway from today's class is that economic analyses are essentially make-believe. There's no real way to measure cost to society. So, if you really want to get fiction published in the peer-reviewed literature, call it "economic analysis". I respect that that's probably unfair. I'm sick, and Fonzie is hungry.


*Seriously. This is a man working on making spitting cobras airborne and contagious. Yes, when venemous snakes spread like viruses, person to person, it's pretty awesome, and it elevates bio-warfare to an elegant new art. I grant you all that. But have you considered that the anti-bodies to these organisms aren't fully reproducible outside of lab-mice the size of rhinoceroses?

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