Clinically relevant diagnostic research in primary care: the example of B-type natriuretic peptides in the detection of heart failure.

With the emergence of novel diagnostic tests, e.g. point-of-care tests, clinically relevant empirical evidence is needed to assess whether such a test should be used in daily practice. With the example of the value of B-type natriuretic peptides (BNP) in the diagnostic assessment of suspected heart failure, we will discuss the major methodological issues crucial in diagnostic research; most notably the choice of the study population and the data analysis with a multivariable approach. BNP have been studied extensively in the emergency care setting, and also several studies in the primary care are available. The usefulness of this test when applied in combination with other readily available tests is still not adequately addressed in the relevant patient domain, i.e. those who are clinically suspected of heart failure by their GP. Future diagnostic research in primary care should be targeted much more at answering the clinically relevant question 'Is it useful to add this (new) test to the other tests I usually perform, including history taking and physical examination, in patients I suspect of having a certain disease'.