A Bug in Our Blood: A Conversation with UCSF Health Economist Leslie Wilson

By Jeff Miller

Photo of Leslie Wilson

Leslie Wilson

Every two seconds, someone in America needs a blood transfusion.

It’s not something we think about much, unless we happen to manage a blood center or organize a blood drive.

But this river of whole blood, red blood cells, platelets and plasma is what keeps millions of us alive when surgery, trauma or disease threatens our existence.

No wonder, then, that keeping this supply free of infection is so important to public health.

Of course, safety costs money. And as UCSF health economist Leslie Wilson, PhD, has learned, when it comes to finding unexpected blood-borne infections like Chagas’ disease with new tests, spending $22 million to save an estimated 2,000 lives is more than worth it.

But even now – with evidence mounting that a surprisingly large number of American blood donors are carrying the so-called “kissing bug” disease – the screening test is not mandatory.

Why that is and what health economists can do to speed change have made Wilson an expert in both dollars and common sense.

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Podcast transcript

Jeff Miller: Hello, I’m Jeff Miller, welcome to Science Café. I’m here today with Leslie Wilson, a professor of health economics and policy at the School of Pharmacy. Welcome Leslie.

Leslie Wilson: Thank you very much.

Miller: Leslie specializes in health services research and economic analysis of disease and the treatments for disease which I guess is a nice definition for health economist, but how does one become such a person, and maybe you could tell us why?

Wilson: OK, Well, I started out in the health care field in practice, and then found that a lot of decisions about what health care was given to patients depended on how much that treatment cost. Some of the newer treatments seemed like they cost a lot of money in the beginning, when you had to pay for them, but sometimes they saved costs downstream.

Miller: Is that always obvious?

Wilson: No, it’s not obvious, so a health economist will look at that and they’ll go weigh the value of the treatment from the perspective of both the cost and the benefits of the treatment.

Miller: How do you actually get that kind of information?

Wilson: You can do studies to look at it; you can measure all the effects of a particular treatment and all of the costs that go into providing the treatment as well as the savings that are provided from shorter hospital stays, or going back to work earlier, or things like that.

Miller: So how long have you been a health economist?

Wilson: For a long time, 20 years or so-

Miller: How has the field changed? Were you alone at the beginning?

Wilson: There were fewer at the beginning. Now it’s pretty common to have health economists in drug industries and managed care systems and also in universities as well working on health care.

Miller: And so this corresponds with the rise in health costs - everyone has an interest in finding out what is causing them?

Wilson: Exactly, yes.

Miller: There are a lot of studies funded both by pharmaceutical industries as well as other professions and industries...

Wilson: Yes, though NIH will fund some purely economic studies but they could fund more, I think. They sometimes expect it to be attached on to other studies, which is sometimes appropriate, but we could speed this along more if we had more funding.

Miller: So give me an example of the kinds of things you’ve studied. I’ve looked at your resume and I’ve seen some publications on everything from teaching of cultural competence, to the cost of different prostate cancer treatments. Let’s talk about the wide range of things you’ve studied over the 20 years.

Wilson: Mostly I’ve studied in three sort of big areas: one area is to look at the cost-effectiveness of new technologies, and so this relates to new products or drugs or testing in different disease, and mostly I’ve worked in the area of cancer – looking at GI cancers, also in prostate cancer and other cancers, also in rare diseases, I’ve looked at scleroderma and some chronic obstructive pulmonary disease (COPD), which is rare in some instances…

Miller: So when you say technology you’re actually talking about everything from a surgical technique, to a drug therapy, to what?

Wilson: Yes, all of those things, like for example, one study looked at the use of neuromonitoring during ear surgery, to see if that reduced the risk of facial paralysis with surgery.

Miller: What did you find in that case-

Wilson: It did. It was very cost-effective to monitor everybody during ear infection surgery, to reduce the risk in just the few who do get those paralyses.

Miller: Have you ever done a study where the cost – I know you deal about cost benefit ratios – where it just seemed so ethical, even if it did cost more, it was something that absolutely needed to be done to protect the patient, that might not have been done?

Wilson: Yes. You look at both the ratio of cost-to-benefits, but you also look at the magnitude of the benefit as well, because there are some cases where the benefit is so big that you would want to do it regardless of the cost-benefit ratios. HIV Treatment at the very beginning is an example of that. And a lot of political pressure allowed some of those early treatments that weren’t very cost effective to go forward.

Miller: Let’s talk about cultural competence for example, can you tell me something about that study?

Wilson: We were asked by the state to look at the amount of cultural competence that was being taught in California medical schools, dental schools, and also pharmacy schools. And this was in relation to the need to approach the care of mostly-Hispanic patients in a cultural competent way. And they were looking at all types of proposals of policy to deal with this. So I looked really at just what level of teaching occurred in our medical schools and our pharmacy schools to see if those graduates would be prepared to deal with and treat Hispanic patients-

Miller: So you’d be looking at the cost of training them vs. the-

Wilson: I didn’t look at cost in this case, I just looked at the health outcome.

Miller: I see.

Wilson: So sometimes I’ll look at one side or the other, instead of both together, and the next step would have been to look at the cost of different kinds of proposals.

Miller: So it’s not always about dollars?

Wilson: No, it’s not always about dollars.

Miller: What did you find in the case of cultural competence, out of curiosity?

Wilson: I looked at both private and state-funded schools and it looked like state-funded professional schools had more cultural competence, and a lot of it depended on how many culturally varied faculty were in the programs as well.

We also found that the students had many courses in this area, if you included their practice sites. Many schools had practice sites that included underserved areas and a lot of those were run by the students themselves. So they seemed very sensitive to that.

Miller: Let’s move on to prostate cancer treatment. Obviously this is a very important topic today…

Wilson: Yes it is, and there are a number of different treatments for prostate cancer, ranging from just active surveillance, or watchful waiting, to surgical radiation, also some hormonal treatments as well.

And a lot of these are based on what kind of patient you are, what age you are, how soon your tumor was found, all of those kinds of things and so your treatment would depend on that. And what we did this time was just look at the cost piece of this, and we compared costs of all these different kinds of treatments.

Essentially what we found is that the treatment costs did vary, but they varied more on the severity of the patient than they did on the difference of the treatment. So we concluded that some previous studies that showed that you shouldn’t do some treatments because they were too costly, were really only costly because they were treating the sickest patients, therefore people should still select treatments based not on cost, but on what was most appropriate for their treatment given their condition.

Miller: And when say ‘people’ you’re talking about established medical care providers.

Wilson: Yes. And they’re doing that now, but we didn’t want to have changes in that approach based on studies that erroneously really just looked at just short-term costs, and didn’t account for some of the age and severity factors that we were able to do.

Miller: How is the information gathered actually used. There is no requirement that when you find x, that x is actually implemented in the marketplace, correct?

Wilson: No, and that’s partly the responsibility of the researcher to try to disseminate this research, through publications, but also through talking to other people. The cultural competence research was written up of course, but also, I gave a presentation to the committee that was reviewing those kinds of treatments.

I also did a study for worker’s compensation, and they actually used the results of that study in writing some of their regulations, and we were able to help them with that. So many times there’s a very direct response, and sometimes less use of it, of course.

Miller: Speaking of presentations I know that you made one about the safety of California’s blood supply as it relates to Chagas’ disease, which, for some of you who don’t know what Chagas’ disease is, it’s a parasitic disease, correct?

Wilson: Right.

Miller: Mostly found in Latin America, transmitted by an insect bite…

Wilson: Yes. This is a disease which is in about 10 to 16 million people in Latin America, including Mexico. This is Central South America and Mexico, and, it’s usually contracted –if you live there- when you’re young, and by a bite, a beetle, or just kind of a bug that looks like a beetle. It bites you and then it actually defecates in the wound that it has made in you, and it itches and you scratch it into the wound.

Miller: And they have a particular affinity for the face I understand – sometimes called “kissing bugs”?

Wilson: Yes, and there’s a characteristic swelling of the eye that is seen, but the bug can actually bite you anywhere. Only about five percent of the people get sick with flu-like symptoms when they first get the bite, and a lot of times it’s not identified as a Chagas’ bite, and so they don’t get treatment at that time-

Miller: I want to stop you right there – what would the treatment be?

Wilson: There are two drugs, Besmidasol and nefurtimox, and those treatments are sort of difficult treatments because they have side effects, but they’re pretty effective if you give it right away when they get the infection.

Miller: Are they expensive?

Wilson: They’re not too expensive but they’re barely available. One company has stopped making the drug, and it’s only available from the CDC. And the other company that makes it wants to stop making it but it’s just making it, you know, for awhile. So

Miller: Is it being distributed in the areas where it’s actually occurring?

Wilson: Yes, but it can be hard to even get in those places in the future so people are concerned about that as well.

Miller: So even if you were diagnosed there might not be a drug available to treat you…

Wilson: Well there is right now, but I hope there is some awareness that we need to continue to have these drugs available. So I think that’ll happen in light of the new studies that have gone on in the blood supply.

Miller: Let’s just say the person is infected. What happens, because there’s an acute phase and then a chronic phase – this doesn’t go away…

Wilson: Right. There is an acute phase, which is what I just talked about, the flu-like symptoms, but mostly those aren’t identified, then people go into sort of a latent phase, where they have no signs or symptoms they’re aware of, of the disease, and then about 30 percent of the people, in 10 to 30 years, develop severe chronic symptoms of the disease.

Miller: And that would include,

Wilson: And that includes mainly symptoms of heart disease, congestive heart disease, and conduction difficulties of the heart where often the first symptoms are sudden death from cardiac causes where your conduction system stops working. Or you gradually get an enlarged heart and congestive heart failure. Also there are swellings in your gut, where your whole digestive tract loses its innervation, and therefore there is severe constipation and bloating – so serious that you have to have surgery and people can die of that symptom as well.

Miller: So what does this have to do with the blood supply in California?

Wilson: Well, in Central and South America, it’s mandatory to test the blood for Chagas’ disease because Chagas’ disease can be transmitted through the blood system as well and so the prevalence of Chagas in those countries is fairly high, so it’s important that this not also be transmitted in the blood. In Mexico it’s voluntary to test, so they test a lot but not everything, and in the United States there was no testing until just recently. In December of last year a test was approved for the first time to be able to screen for Chagas in the blood supply, and they began to test in about 65 percent of the blood starting January first of this year. So now our blood system is being tested.

Miller: So you were asked to determine the prevalence of Chagas within the blood supply?

Wilson: I started the study before this testing, to try to identify what the risk might be of Chagas in the blood system to encourage testing, actually. We started the test a year-and-a-half before the drug was approved, and we surveyed patients in five blood systems in California and asked them about risk factors that they had, in terms of where they lived, and what kind of housing they were in because these bugs like to hide in thatched roofs or cracks in the wall and things like that, and whether they’d received blood in those areas where they could have risk of contracting it that way – or if they had a risk from birth, from a mother who had Chagas, because that’s another way of transmitting.

So we surveyed these people and identified what the risk would be based on where they lived essentially. And then we also asked them a lot of other information about general health to identify if they had Chagas’ disease currently.

And finally we looked at the cost-effectiveness of different screening methods for implementing a blood testing system should this test, which now has come to pass, begin. So we looked at those areas.

Miller: And what did you find?

Wilson: Well, at the beginning when we just looked at the risk, we looked at three kinds of blood system areas representing three types of locations: One, was in San Francisco, which was sort of a mixed city, and also in San Diego, which is close to the border, and so you would think would have a high risk of Hispanics, or Latin Americans, coming across the border, and then we looked at a more agricultural area in Modesto, and areas around there.

And what we found was that the risk varied of course across these three sites, but not necessarily how you would expect it to vary from the prevalence of Hispanics, self identified, in the community. And so we found that San Diego was relatively high risk according to the survey questions, but that the agricultural area was not very high, and San Francisco was surprisingly high.

Miller: Why do you think that happened?

Wilson: The reason was primarily because everybody in the population is donating blood, so some of the people in the agricultural areas were newer immigrants and were not yet donating blood, whereas the longer someone has been here we think the more likely they are to donate blood, and so therefore more established Hispanic communities are probably donating more. So one thing is, you can’t assume from the population, that that’s also the population that is donating blood, the other thing is there are many people from Latin America who consider themselves more of European descent and don’t self identify as Hispanic, and that may be the case in San Francisco area because most of the risk was from Latin America.

And if you’re from Latin America you probably have a higher risk of getting Chagas because it’s more prevalent there, than if you’re from Mexico. So, even thought there were fewer numbers of people with risk potential in SF, they had a higher prevalence level of risk, being from Latin America.

Miller: When you looked at all this data where you able to determine either a presumed degree of risk, or an actual level of infection in the blood supply?

Wilson: Well we were only able, with these survey instruments, to get a level of presumed risk, and then this level was compared with the levels that are being obtained now that testing has begun in January.

Miller: And are the two in correspondence, or are the results of the real test not available yet?

Wilson: The very first test for the drug approval looked fairly low, and much lower than what we had estimated. When we looked just at people who lived, or were born there, then our risk level from these surveys, was similar to the risk level in those early studies.

But now, it seems as they’re testing more people, that the risk level has gone up, and it’s something like one in seven thousand in Los Angeles, and one in 30,000, sort of in a 30 state area around the U.S., and that’s something like 250 Chagas positive people that have been found in the blood supply across the U.S. from January to October.

Miller: So, should we be reassured that these tests are keeping our blood supply safe, and then, there’s costs associated with this obviously, so if it’s determined that to prevent this from becoming lodged in the larger population, do the people managing the blood distribution think the test was worth the cost?

Wilson: I think that they’re somewhat surprised that they’re getting high numbers in some cases, even though with the increase in immigration people were beginning to get more and more concerned as the years went by. But I think it’s very good that we are testing now, and it should be remembered that what we’re looking at is donors who are positive, and they’re donating blood that has the potential to pass on Chagas disease, but not all of that blood will actually transmit the disease-

Miller: I want to clarify that right now – so let’s just assume that you’re unlucky and you happen to get some blood from an infected donor, is it automatically true that you’re going to get the disease?

Wilson: No it isn’t, and we don’t really know what the risk of transmission is, it may be as low as 10 percent – I know in Latin America it’s as high as 30 percent, so we're not certain whether it’s the same in those countries or a little bit different, a little bit less, maybe because the health of the people is better or something like that.

So we don’t know, but we don’t really want to transmit that in the blood system anyway.

Miller: Are there any other features of the study that we should know about, that you found particularly interesting?

Wilson: I think what’s important now is, first of all, not all blood centers are testing, and individual blood centers are trying to decide whether to test, and that’s where our cost effectiveness study, I think, was important, and also our result, that you can’t tell from the population around you, what your real risk is, so people that may think they have very low Hispanic rates according to that population study may in fact have some more risk than they know about. So, I don’t think you should decide on that basis.

In addition we found that, when we looked at a very broad risk through a screening question, which is just ‘have you ever lived or traveled to South America or Mexico’ and ‘were you born to a mother who has,’ we found that about 30 percent of the people say yes to that question. So blood centers need to decide whether they’re going to test or not, and how many people they’re going to test.

So we suggest, that the maximum you would have to test might be 30 percent of your blood supply if you ask a screening question, and this could reduce the cost of testing everyone. What we did was we looked at the cost effectiveness of three kinds of testing approaches: testing everyone with this new Eliza screening test, or only testing those who screened positive, compared to testing no one, which was the previous policy.

And we tested this with three levels of risk of Chagas disease, depending on what kind of risk that you had. And in general we found that testing everyone was cost effective compared to testing no one. Also, screening first, with this verbal screening test, and then just testing those positives, was also cost effective compared to testing no one.

So, regardless, it’s better to test some, than no one. So all blood centers should at least do that.

Miller: And effectiveness would be determined by lives saved, perhaps?

Wilson: Yes, we looked at lives saved. And that involves what proportion of the people are likely to get Chagas disease and then have to incur the treatments of Chagas disease, which can be 10 or 15 years of treatments of serious health effects. And then, eventually die from Chagas disease or other causes we had in our model too.

Miller: From a consumer’s point of view then, what can be done to protect yourself when you know that you might be in a situation where you’re going to receive blood from a transfusion – do you insist that the blood come from centers where Chagas has been tested for? Can you even determine that?

Wilson: Well, many times people can self donate for themselves if it’s an elective surgery, and that’s always a good idea, or have someone they know in the family to donate blood for them. So that’s one thing people are already doing when they can, but many times you cannot do that, and you’re in a trauma situation and you just get blood. In that situation, I don’t know if you’re in a position to be asking that question.

But I think it’s important for the public to be aware of this, and maybe when they’re donating blood, it’s important to be clear on what answers you give when you’re donating as well, and to mention this in blood donation centers as well.

Miller: One last question: so who decides whether or not all the centers that are taking blood actually incorporate this test for Chagas disease?

Wilson: Well, the FDA looks at this, and of course the blood systems too, the American Red Cross and the American Blood Systems, and those are the two places that are testing all of their centers, and that’s about 65 percent of the blood supply, so they’re already testing.

But the FDA has not made it mandatory at this point. They can make it mandatory but I think that they are looking at the early studies which are showing what the risk is first, before they decide whether they should make it mandatory.

Miller: How long will that take, do you suppose?

Wilson: We’ve just had the AABB meeting, which is the American Association of Blood Banks meeting, and that’s where all the researchers and also the people who work in the blood banks get together and review data, so I would imagine that this was the first data that came out and the first discussions of that and so I would imagine that new guidelines would be issued based on that. And we have cost effectiveness results now which show that it is cost effective to at least screen verbally first, even at those places that think they have no risk, and just test those that do. So I think that could be an appropriate approach.

Miller: Well let’s hope they follow your lead. Thank you Leslie for joining me on Science Café today, keep up the good work.

Wilson: Oh, thank you very much, it was fun.