Kees Jansen, MD

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Dr. Kees Jansen:  “At present we are at the  European Society meeting in Lausanne in 2001.  We have just heard a very  interesting lecture by Dr. Hajo Wildschut who is sitting next to me,  and my name is Kees Jansen.  This lecture was such that I would like to  interview him on some of the important messages he had to convey.  Now,  Dr. Wildschut, could you tell me something about, for instance, the  difference between prenatal diagnosis and screening?”
       
       Dr. Hajo Wildschut:  “Yes, thank you very much.  Indeed, I think  with the influx of all new medical technologies there is a tendency to  use diagnostic tests in screening settings, and I try to make a point  that you should carefully interpret your test results in a screening  setting because they’re not necessarily the same as in a diagnostic  setting.  This sounds fairly complicated but to cut it short, when you  have a positive test result in a screening setting that doesn’t mean  that you have the disease since the likelihood that in a screening  setting the woman has the disease is very low, and I’m talking about,  for example, infectious diseases like chlamydia.  You should really do a  diagnostic evaluation of positive screening tests - an office positive  test results - in a screening setting to rule out or to confirm disease.   That’s very different from when a patient comes in to your office with  symptoms or signs of, for instance, infectious disease because when the  test is positive for chlamydia then the likelihood that you will indeed  have chlamydia is very high.  So one of my thesis during this lecture  was that you really have to know the pre-test probability of the disease  prior to testing - so are you looking at someone who’s coming from a  screening setting or someone from a diagnostic setting like your own  clinic.”
       
       Dr. Kees Jansen:  “I think that’s a very important message because  the outcome is determined by the patient population that you’re looking  at.  Now one of the other things that struck me in your lecture is  that, let’s say, the sensitivity and specificity of the test, the value  of it, and the number of false-positive and false-negatives is very much  dependent on the incidence of the disease itself in the population you  have.  Would you comment on that for me?”
       
       Dr. Hajo Wildschut:  “That’s very right, you have a fairly good  test and using that in a diagnostic setting then, indeed, the likelihood  that you have the disease is high.  However, using the same test with  the same sensitivity and the same specificity in a screening setting  then the likelihood that you have the disease is low.  I think many  people don’t realize that and that’s the point I try to make assuming  that the sensitivity and the specificity of these tests are similar in  each setting.  However, quite often in screening settings the  sensitivity and specificity are even worse so you should be very, very  careful with the interpretation of test results from screening settings.   People might say - why don’t you use a better test that tests up to  99% sensitivity and 99% specificity and those tests are indeed available  in diagnostic settings, however, these tests are quite expensive and  when you go to asymptomatic women you have a very large population  because most of the population doesn’t have any symptoms.  The disease  prevalence and the ones you see is a smaller number so what happens if  you use those expensive tests for screening purposes then the costs per  case detected goes up substantially, and I think that’s also a very  important message.”
       
       Dr. Kees Jansen:  “So basically it all boils down to the amount of  money we as a society would be willing to spend on a test and the other  thing, of course, is the percentage of unrest that you may create if  you cut costs.  If you have a cheaper test, a number of patients will be  alarmed by a false-positive test, which is very much independent on the  sensitivity of the tests as such.  Are there some other remarks you  wanted to talk about?”
       
       Dr. Hajo Wildschut:  “I think you’re right.  I didn’t talk about  that during my lecture, but you have to follow the WHO criteria of  Wilson and Jungner.  One of the first points they make in order to  provide money for tests like this is the importance of the health  problem, and when is a health problem important?  I think that depends  on two things.  One is it’s important when you have a severe disease  which affects the health of the particular person and, secondly, it’s  important when it’s highly prevalent.  We often talk here at these  settings about rare diseases so, indeed, the Wilson and Jungner criteria  for importance are fairly subjective.  I think we have to discuss in  the community and assign money to those health outcomes which we  consider as important not only in terms of severity of the disease  outcome but also in terms of the likelihood of the disease occurring.”
       
       Dr. Kees Jansen:  “Thank you very much.”
       
       Dr. Hajo Wildschut:  “You’re welcome.”

Articles

OBGYN.net Conference CoverageFrom the ESHRE 2001 Conference - Lausanne, Switzerland

Screening Settings VS. Diagnostic Settings

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Author | Kees Jansen, MD

Articles

Screening Settings VS. Diagnostic Settings

Screening Settings VS. Diagnostic Settings