A key feature of a self-collected HPV testing strategy is the move of the primary screening activities from the clinic to the community whit the efforts to increase the affordability and availability of HPV DNA tests.Within the self sampling project,ongoing in ISPO, Florence, women aged 35–64 years,residents in Florence, who had been invited,by the screening programme,in the past screening round and had failed to respond were eligible for the study. A random sample of 5200 eligible women was randomly assigned to one of the following arms:control arms with a standard invitation letter to perform HPV test at the clinic on a pre-fixed date; two intervention arms: a group was directly sent the “home based” dry self-sampler device (nylon FLOQSwab® Copan,Italy) another group was directly sent the “home based” self-sampler device (nylon FLOQSwab® Copan,Italy) and 1 ml of preservation and transport solutions (MSwab® Copan,Italy). As a prerequisite for carrying out the study,we have investigate sensitivity and reproducibility of HPV test, carried out on Cobas®4800 (ROCHE®) in HPV16 plasmid samples obtained by swirling the FLOQSwab® in ThinPrep®(TP,HOLOGIC®) and in MSwab®+TP®.
Starting from HC2® (Hybrid Capture®2,QIAGEN®) high risk calibrator (plasmid 100 HPV16 copies/μl) we prepared a series of dilutions in TP® and MSwab®+TP® (rate 1:4). For each test, calibrator was absorbed on FLOQSwab® and then swirled in assay preservation solutions. For each sample clinical sensitivity (5000 HPV copies/reaction) and LOD (Limit of Detection) were evaluated in 20 replicates comparing the results with Roche LOD (600 copies HPV16/ml). FLOQSwab® adsorption was taken in account in order to guarantee the actual copies number.
All 12500 HPV16 copies/ml (5000 HPV 16 copies/reaction) replicates in MSwab® +TP® and TP® are positive. Only 65% of 600 copies of HPV 16/ml replicates in TP® and 60% in MSwab®+TP® result positive. It was found that LOD is 1200 copies of HPV16/ml, since all replicates in MSwab®+TP® and 95% of those in TP® are positive. FLOQSwab® adsorption was about 230 μl.
FLOQSwab® LOD for HPV16 is 1200 HPV16 copies/ml. Compared to LOD provided by Roche, results show that FLOQSwab®, retained part of the viral load,shows a higher LOD. However near to the clinical sensitivity limit, FLOQSwab®'s performance was as expected. Against this different FLOQSwab® performance, the MSwab® analysis buffer has been shown to have good performance, both for much lower and at the limit of clinical sensitivity viral loads. From the results reported, it appears that MSwab® has a slightly higher analytical sensitivity than TP®, which could however result in a lower clinical sensitivity.