(P319) VIVALSTI: In-vitro validation to assess the effect of sample transport of home-based self-collected samples on the detection of blood borne sexually transmitted infections.

Background: Online HIV/STI testing (i.e. home-based self-sampling and shipment via regular mail to a certified laboratory) is becoming increasingly important globally. However, before online HIV/STI testing can be implemented in regular care, an in-vitro laboratory validation of several transport conditions is needed to investigate if these conditions influence diagnostic assay performance characteristics.

Methods: EDTA venous whole blood samples were collected from patients, with a known HIV, syphilis and hepatitis C virus (HCV) serology status. Aliquots of 1 mL were created and tested at different storage time points (baseline, day 4, 7 and 10) and transport temperature conditions (room temperature (RT, 19-23,5°C), 2 to 8°C, 30°C and fluctuations between 2 and 30°C) to mimic different transport conditions. For each parameter, minimum 7 positive and 3 negative samples were tested with different serology assays (table 1) including the haemolysis index.

Results: Overall, a stable trend was seen over time for the positive quantitative results for all parameters (Table 1). There was no apparent proof of loss in sensitivity in any tested condition. Except for the Vitros HIV Combo test (Ortho Clinical Diagnostics), the final interpretation of the negative samples remained the same for all assays. However, we noted an overall increase in ratio over time for most of the Vitros assays, starting at day 7 and day 10 and for all temperature conditions, except 2-8°C. Strong haemolysis was seen after 7 days.

The final result of the RPR and Geenius assays remained the same for all transport conditions, however, a two-fold decrease in titer in the RPR assay was noted in one sample (at day 7 for 2-30°C and 30°C and at day 10 for all conditions). The titer remained rather constant (±1) for the other conditions.

Conclusion: Samples for HIV/STI testing should be analysed within 7 days and temperature should ideally not rise above RT to avoid false positives and unnecessary supplementary tests. Despite limited sample numbers and without included weak positives, there is no apparent loss in sensitivity for any of the condition/parameter combinations.