In this article, we would just like to raise awareness for a terminology issue which is prone to cause imprecisions and misunderstandings in communication between CROs, biobanks, and IVD manufacturers.
While the terms ‘prospective’ and ‘retrospective’ are part of everyday language in the pharmaceutical industry, they have gained some importance in the IVD sector as well since the implementation of the IVDR and related secondary legal acts. With stricter requirements regarding validation study design and sample quality becoming the rule, it is about time that these terms are used with appropriate precision.
‘Prospective’ and ‘retrospective’ are used when discussing sample procurement and study design. Their meaning in sample procurement, however, is not synonymous with their meaning in study design!
In discussions with sample procurement experts, the term ‘retrospective collection’ is often used when referring to a collection of leftover and usually frozen samples, and the term ‘prospective collection’ when referring to a collection of fresh samples specifically for a particular project.
This is not synonymous with the terms ‘retrospective study design’ and ‘prospective study design’. In a retrospective study, the inclusion criterion for potential donors or samples would be a known clinical condition, e.g., through a test result or diagnosis. In a prospective study, donors or samples would be selected based on a medical indication that corresponds to the intended purpose of the index test (the device being evaluated), e.g., the presence of certain symptoms or being part of a risk group.
This means that we could easily combine these terms counterintuitively: We could conduct a retrospective study using prospective sample collection, e.g., when fresh blood samples are drawn (‘prospective collection’) from donors who are known HIV-positive (‘retrospective design’). Conversely, if we were to take frozen leftover samples (‘retrospective collection’) from donors of which we only know that they were treated for suspected deep vein thrombosis (‘prospective study design’), we would be conducting a prospective study using retrospective samples.
This being said, reality shows that these two meanings are often confused. For instance, when we suggest a retrospective study to a customer during a call, we oftentimes get the response that the customer would prefer freshly drawn samples. The ensuing clarification is time-consuming and can be confusing or irritating, and we hear similar stories from our partners and competitors who also offer consulting services in the IVD sector. Awareness of the overlapping but not congruent definitions of these important technical terms will lead to more efficient and precise communication between CROs and sponsors.