Archive for June 2009
This post follows up on an earlier one concerning the value of mathematical models, computer simulation, and operations research in dealing with pandemic and inter-pandemic (seasonal) influenza.
There’s a lot that can be done to control flu, once its known to be spreading. We can shut down a school, for example. But the key is to suit an intervention precisely to the need, and not to overreact. We can shut down *a school*, and not all schools in an entire city or country.
To accomplish such tailored intervention, information is crucial: we need to know who actually has the flu, and what strain of flu they have.
A current problem is that the majority of flu cases are not formally diagnosed. People get flu-like symptoms; they suffer for a week; they get better — and that’s that. Then they tell people “I had the flu”. Yet many of these people might not have had the flu at all. They may have had a cold, or food poisoning, or some other infectious disease.
Fortunately, fast, simple, and potentially inexpensive tests exist to diagnose flu and to identify viral strain class (e.g., A or B strain) exist. However, currently, these tests usually require a visit to the doctor.
As a result, only a minority of people with the flu receive a test. First, why visit a doctor in the first place? You’re sick in bed, suffering from symptoms. The last thing you want is to get into a car (much less a bus) and visit a doctor. Besides the inconvenience, that stress is harmful (remember, the classic treatment of flu involves staying in bed getting lots of rest). Further, by traveling and sitting in a doctor’s office reception area one risks contaminating other people.
Many doctors will not request a flu test anyway. Why should they? It’s added cost and inconvenience. And from a clinical management standpoint, a confirmed diagnosis of flu is of little value. In most cases the treatment is the same: stay home, rest, and drink fluids.
Note this is different than for bacterial respiratory tract infections; there one wishes to identify the bacteria in order to select an optimal antibiotic.
Potentially a flu test could be of value in deciding to prescribe Tamiflu. However, Tamiflu has a short window of efficacy. If a doctor suspects flu, then the logical thing would be to prescribe Tamiflu immediately, rather than wait for the results of a lab test.
Recall what happens with a flu test. A cotton swab is inserted into the nasal passages, collecting a mucous sample. The sample is then sent to a lab for processing. It could take a day or longer for the sample to reach the lab. Then it might wait several hours before processing. And then it might take another several hours for someone to phone or fax the results to the doctor. By that time the window of opportunity for Tamiflu would have potentially passed.
A Paradigm Shift
What we need to recognize is that the real value of flu testing is not to benefit an individual patient, but society. That is, the main value is epidemiological, not clinical.
A flu test should be routinely performed so that we can track the spread of flu virus during an outbreak and to make judicious interventions on that basis.
Because of this, we should consider paying for flu tests out of the public coffer, instead of billing patients individually. Further, we should consider streamlining the flu assay process. Here are some suggests towards that end:
1. Develop even faster, cheaper tests. The tests are already simple. A flu antigen test can be performed in 15 minutes, using paper tabs, analogous to a home-based pregnancy test. However, currently these are performed in a lab, by a trained technician. The costs are not currently stated online, but a reasonable guess would be at least $50. What would be ideal is a home-based test, purchasable at a local drugstore. With many more test units being sold, one could easily imagine the price dropping to $10 or even $5 without loss of total revenue to manufacturers.
2. Mobile flu test units. It might take a while to overcome institutional resistance to a home-based test. In the meantime, we could in the US develop something that is already common in Europe: lab courier. Lab couriers are people who can come to your home and pick up a something like a urine sample and take it to the lab for processing.
Option 1 a no-brainer. Eventually this will likely happen. The only question is when. Again, there is probably institutional resistance to overcome. In a sense, this takes work away from doctors and labs.
Option 2 requires a little analysis however. All the parameters involved are straightforward. We can estimate how many people would use such a service (hopefully, if the cost is low enough, nearly everyone with suspected flu). We can also estimate the potential value to society. By tracking the spread of a flu outbreak with almost complete accuracy, we could issue local alerts, close schools, etc. We could optimally distribute antiviral drugs, and launch rapid-response immunization programs. We could also prevent hysteria and unnecessary closures. By tracking an outbreak with complete precision, we could potentially prevent a pandemic.
How much would that be worth? To judge from government investments in bird flu contingency plans, billions of dollars.
The question is whether a publicly financed mobile flu-test units, or some other innovative program, would be cost-effective, in terms of saving money and reducing morbidity and mortality. These are, in principle, simple calculations to make, and perhaps someone at a public health school or the CDC will run them!