P114 A New Method for Self-Collection of Blood Specimens for HIV Pre-Exposure Prophylaxis (PrEP) Laboratory Monitoring

Cannon, C.; Malinski, C.; Golden, M.

Sexually transmitted infection (STI) testing is an important component of PrEP care. Home-based PrEP monitoring (HBPM), consisting of STI sample self-collection and remote follow-up, could improve PrEP access and retention rates, particularly in the context of the COVID-19 epidemic. However, existing fingerstick methods for collecting blood often result in too little specimen for quantitative rapid plasma reagin (RPR) testing, limiting the ability to distinguish between old and new syphilis infections. We evaluated the Tasso OnDemand™ device, designed to collect 300 μg of capillary blood, for self-collecting blood specimens for PrEP monitoring, including quantitative syphilis testing.From July 2020 – January 2021, we enrolled 46 clients who were either on PrEP, had known/suspected new syphilis infection or were living with HIV and seeking STI care at a sexual health clinic in Seattle, WA, USA. After brief instruction, clients used the Tasso device in the clinic to self-collect blood from the upper arm. We compared HIV antigen/antibody, quantitative RPR and creatinine assay results using paired Tasso and venipuncture serum specimens.Most clients were cisgender men (42/46, 91%) and currently using PrEP (33/37, 89%). Of 46 participants, 40 (87%) collected a blood sample sufficient to complete ≥1 test. Percent positive agreement and negative percent agreement (PPA and NPA, respectively) for 34 HIV specimens was 100% (7/7 HIV positive). Of 30 paired qualitative RPR specimens, PPA was 100% (10/10 samples) and NPA was 95% (19/20 samples). Differences between 9 paired quantitative RPR titers were all ≤1 dilution. Paired creatinine results (n=9) were strongly and positively correlated (r²=0.84, p=0.008) with a median difference of 0.05 mg/dL (range: -0.01–0.20).Self-collection of blood specimens adequate for recommended PrEP laboratory testing is feasible and results show high levels of agreement with venipuncture samples. The Tasso device shows promise for use in mailed sampling kits for HBPM.