Evening lecture by Prof. Dr. Mariska Leeflang, organized by the 'Chemische Kring Zwolle'.

From home test to hospital laboratory: (non)sense, fact and myth

Summary
In recent years, newspaper headlines have regularly featured stories about new diagnostic tests for Alzheimer’s or Parkinson’s, or tests that can detect several types of cancer at an early stage from a single drop of blood. The research on which such reports are based is often distorted or presented in a more positive light than the results warrant.

In this lecture, I will discuss a number of aspects of this type of research:

1. Research into and evaluation of diagnostic tests and biomarkers follows a cycle of questions, ranging from ‘is there a link between this measurement and the disease?’, through ‘can this test distinguish between people with and without the disease?’, to ‘if people undergo this test, are they better off than if they do not?’.
2. The value of a diagnostic test depends heavily on the setting within the healthcare system in which it is used. This setting determines the characteristics of the people being tested and, consequently, the accuracy of the test. It also determines the next steps and, therefore, the consequences of any false-negative or false-positive test results.
3. Many test evaluations are based on healthy volunteers on the one hand, and people in whom the disease to be detected is clearly present on the other. Such evaluations are problematic, firstly because they do not account for the ‘grey area’ of disease; and secondly because healthy volunteers are not usually the target group for a diagnostic test.
4. So, if we want to know the value of a diagnostic test, we need to know where the test is going to be used and whether the study in which the test was evaluated was also conducted in that situation. The problem, however, is that researchers are not transparent in their descriptions of what they have done and who the study participants were.

In summary, I believe we face a major problem when it comes to diagnostic (laboratory) tests: we do not know exactly how well the tests distinguish between people with and without a particular condition. This is because the studies on this subject are poorly reported. News reports about new diagnostic tests should therefore be taken with a large pinch of salt.

Biography
After qualifying as a vet in 2003, I began a PhD programme at the Faculty of Medicine at the University of Amsterdam on the topic: ‘Systematic reviews of the accuracy of diagnostic tests’. I carried out this research in close collaboration with the Cochrane Collaboration, an international organisation dedicated to promoting ‘evidence-based’ principles and to producing and publishing systematic reviews of the literature. Since then, this has been the core of my work: methodological research into the quality of scientific literature, primarily in the field of diagnostic tests. My main message in this regard has always been that the value of a diagnostic test depends heavily on the context in which it is used. With this message, I support a wide range of organisations, such as the World Health Organisation and the Knowledge Institute of the Federation of Medical Specialists, and I continue to support the Cochrane Collaboration.

Invitees are very welcome.

For further information about the lectures, please contact the CKZ by email: ckzsecretariaat@gmail.com.