a novel approach to detect testseeking behaviour in the blood donor population making the invisible visible background and objectives individuals may donate blood in order to determine their infection status after exposure to an increased infection risk such testseeking behaviour decreases transfusion safety instances of test seeking are difficult to substantiate as donors are unlikely to admit to such behaviour however manifestation in a population of repeat donors may be determined using statistical inferencematerials and methods testseeking donors would be highly motivated to donate following infection risk influencing the timing of their donation donation intervals within 20052014 of all dutch blood donors who acquired syphilis n 50 hiv n 13 htlv n 4 or hcv n 2 were compared to donation intervals of uninfected blood donors n 7 327 836 using the andersondarling test we adjusted for length bias as well as for age gender and donation type of the infected additionally the power of the proposed method was investigated by simulationresults among the dutch donors who acquired infection we found only a nonsignificant overrepresentation of short donation intervals p 054 however we show by simulation that both relatively short and long donation intervals among infected donors can reveal test seeking the power of the method is 90 if among 69 infected donors 35 51 are test seeking or if among 320 infected donors 90 30 are test seekingconclusion we show how statistical analysis may be used to reveal the extent of test seeking in repeat blood donor populations in the dutch setting indications for testseeking behaviour were not statistically significant this may however be due to the low number of infected individuals