Ebola Tests: Sensitivity and Specificity

Yesterday's headlines on USA Today included one that stated "Nebraska Patient Cases Raises Questions about Ebola Test."  The reason for this is the fact that the Nebraska patient was a physician treating Ebola patients who came down with symptoms and was tested and found not to be Ebola positive before other clinicians eventually realized (and found in a later test) that the man in question did have Ebola.  If the physician had been treated earlier, it is possible that his outcome--being brought back to the US and treated--may have been different from the unfortunate death he suffered.

I'd like to comment on this because it raises some really important issues about diagnostic tests.  I would have expected to find some previous writing on this, but I do not.  So here it goes.

People either have a condition or do not.  We refer to those who have the condition as positive and those who dont' as negative.  Sometimes it is good to be "positive."  With the Ebola virus, it is obvious that being positive is a very bad thing.

Test results are also positive or negative.  (Some tests are uncertain, but for the time being we will ignore that.)  So, the result at the end of a diagnostic test suggests that a person either has or does not have a condition.

What makes this most interesting is the fact that there are some people who are truly positive and for which the test identifies the person as positive.  Similarly, there are some people who are negative and whom the test identifies as negative.  These are both desirable outcomes.

However, there are also two other groups.  There are some people who are positive whom the test incorrectly identifies as negative.  And there are some people who are negative whom the test incorrectly identifies as positive.  

A test's ability to correctly identify those who are positive as positive is called sensitivity.  A test's ability to correctly identify those who are negative as negative is called specificity.

In different situations, clinicians and policy makes focus on either sensitivity or specificity.  Sometimes it is important not to over identify cases.  If the consequences of being positive are fairly small, there will be future attempts to diagnose, and further identification and treatment is costly, we can focus on making sure to identify negatives properly--specificity.  Or if there are strong negative connotations and stigmas associated with being positive it can be important to correctly identify negatives.

However there are other cases in which failing to identify a positive case can be deadly.  This is true with Ebola.  This is why in other cases sensitivity is critical.  This does not mean that there should not be concerns about specificity.  If we had a lot of people mis-identified as positive this would require an enormous amount of resources and there may be side effects of the treatment.

The main "question" I think we should asking about the Ebola test is whether there is a way to develop a test that is more sensitive.  And quickly.  And if the government can support that and someone can find it, there may be a profit to be made from an innovation for humanity.  

Introversion, Analytics, Storytelling

As part of my position as Vice Dean of Education I get to meet a lot of students who have a lot of issues.  This year, I made it a point to also meet students who don't have big issues but who are, in fact, doing great things for the School at which I work.  So, I arranged a series of lunches with leaders of student organizations.  There were many interesting and fun outcomes of the series of four lunches I had a couple weeks back.

One lunch was notable for discussions of introversion, analytics, and storytelling.  You may wonder how those fit together.  Here is how that came about.

First, introversion.  At this particular lunch there were four students.  Some of the lunches I had were largely student driven around issues that applied either to the specific student organizations or around generic student issues.  Two of the lunches were more driven by discussing issues about research or career interests or personal stories.  In this particular lunch, the fourth of the week, the students all knew that I am a runner.  At some point the discussion transitioned to be about management style and personality types.  As I had been leading the conversation, I started with, "Many people don't believe this, but I tested strongly as an introvert on the Myers-Briggs test.  One of the students looked at me quizzically as I said this--body language that said, "Why would people not believe you?"  This student has a keen understanding of what the MBTI really gets at.  I've heard it described as not whether you like crowds but where you go for "recharging" or where you draw your strength.  Many long distance runners--particularly those who are willing to do the longest workouts on their own-are great candidates to guess they would be pretty strong introverts.  Using that time away to think and recharge.  So, that was interesting point number one.

The other two came when the same student, inquisitive about my change from a faculty member at the School of Public Health to a largely administrative role at the business school asked, "Do you still use any of the skills?  And how do they help?"

I gave two answers.

First, I talked about analytics.  While it is certainly the case that I am interested in different data as an administrator and the types of analyses are different, I still need to be analytic.  That is a skill that dates back to my days as a faculty member.  In fact, I would suggest that it is a pretty fundamental part of my personality and dates at least as far back as the future problem solving exercises that I was asked to participate in as part of the academic enrichment program provided by my school district when I was growing up.

Second, I talked about storytelling.  As someone who writes a blog, I'm sure that readers are not surprised to hear that I would focus on storytelling.  The key is how to link that to both research and administration.  While my research reports were never as gripping as a best selling Tom Clancy novel, good research reports tell stories.  Non-fiction, of course.  But stories nonetheless.  And, as a leader, I have to get other people to move in a direction I want them to.  How best to do that?  By telling stories that illustrate the vision of what I want to achieve.  So, maybe I could have called it communication rather than story telling, but the idea is clearly there.

So, that is how I managed to talk about introversion, analytics, and storytelling all as part of an hour long conversation with four students at the Business School.  And I look forward to continuing to have opportunities to share wonderful and interesting stories about my view of the world with as well as about learning from the students who come to the Carey Business School.  

Affordable Care Act and Strains on the System

This has been an interesting week for issues surrounding health insurance for me.  I was surprised by the amount of the increase in my out-of-pocket premium each pay period for health insurance for 2015.  The explanation was not that all of my employer's health insurance premiums were going up so substantially.  Rather, the main issue was that with my raise, I passed a threshold that led to a higher out-of-pocket premium expectation.  Not completely unreasonable.  Just there.

Then, today, I saw an article in the Wall Street Journal.  The article talks about the link between the Affordable Care Act, expansion of Medicaid, and strains on the health care system.

This is not a completely unexpected result.  There may be other data that I have not seen that counter what I read in the article.  If so, I'd like to see them.

However, the key here is that the Affordable Care Act was designed primarily to do one thing--get more people insured.  At least that was my read of the act.  But I did not read every word, and apparently, at least some involved in designing it thought that the lack of transparency was a distinct political advantage.  (You can see a quote from a fellow health economist here.  The fact that anyone in my profession would make such a statement makes me sad.)

When more people get insured, it takes care of only one part of access--the affordability of care.  And the article in the WSJ even points out that in one state to make sure that new enrollees could be covered by Medicaid, it was necessary to tighten up the management of care for existing enrollees.  That leads to an interesting question about sustainability and the "social utility function."  Is it better to give excellent coverage to a smaller number or moderate coverage with lots of controls to a smaller number.

Additionally, the fact that only affordability changed is showing up in how long it takes people to get care sometimes.  And the waiting list is growing for others to get care as more people who were previously not using anything other than the ER engage in the system.  Predictable--totally.

What does this mean?  Was the Affordable Care Act bad?  That, I believe, still remains to be seen.  Was the law put in place without a holistic view of how to solve the problem of access to health care under budget constraints?  Yes.  Could the United States ever implement a holistic reform?  Not likely given the political environment.

So, while the Affordable Care Act may have solved some problems it has created others.  Does that mean it was worse than no legislation at all?  Hard to say.  Does it suggest there is room for improvement?  Yes.  Where will that improvement come from?  Likely from private sector innovation that finds a way to provide affordable access to care to keep a population healthier while making a profit.  The best way to have a healthy bottom line is to run a business in a healthy community.  This wraps all the incentives together nicely if someone or some organization can figure it out.    

New Technology in Prostate Biopsies

On the professinal side, I am often looking at new opportunities to screen, diagnose, or treat and asking the economic question--what makes this a good buy?  Some, of course, migth simply say, "It is more effective so why would we not want to use resources for it?"  And given the value that is assigned to life, that is often a reasonable supposition.  However, given the limited resources that are available for medical care and public health efforts, it is also often worth while to ask a few deeper questions and determine whether a use of resources is the best use of resources or not.  

On the personal side, my blogging began with a memorial service for a fellow parent at my kids' elementary/middle school who lost a battle with prostate cancer.  So, when there are new ways to guide screening, biopsies, and making a progosis, they almost always catch my interest.

An article in today's Wall Street Journal focused on the potential use of MRI's to guide biopsies to determine whether prostate cancer is agressive and should be treated agressively or whether it is more likely that the tumor, despite its presence, is clinically insignificant.

The article does a good job of describing everything that would go into an economic, cost-effectiveness evaluation without doing one and without, it appears, one having been completed so far.  Specifically, there is a higher cost to have the MRI prior to the biopsy--but from the patient's point of view some of that is paid by the insurer.  There are some aggressive cancers that are detected by the MRI technique and, as importantly, some cases that are rules as "not signficant" after which a patient can avoid being over treated.  Then, to make matters more complicated, there are also a fair number of cases missed despite the MRI.

Thus, an economic evaluation would have to compare the clear and readily identified cost of the procedure (potentially from different perspectives) with the value of more appropriate identification of aggressive cancers and the value of avoiding over-treatment (not just lower costs but potentially better quality of life that results from avoiding the side effects of surger to remove the prostate like incontinence and sexual dysfunction, and then account for the costs associated with still missed cases.

This would not be a simple analysis.  And while we may have quality of life and life expectancy measures for each of the resulting outcomes, this is a complicated situation in which the fear of a missed case or the disappointment with finding out that the cancer was not as bad as expected should be taken into account.  These types of quality of life issues are dynamic and complex.  

How should a decision be made?  The technology has some distinct advantages.  These should be presented to patients.  However, this does seem to call for shared decision making between the patient and urologist with as much information as possible shared in a way that is comprehensible until there is clear data to suggest whether the MRI is truly economically preferred.