Careful with the terms ‘prospective’ and ‘retrospective’ – Are you referring to study design or sample procurement?

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.