O3-17. Decreasing HIV-1 incidence and undiagnosed HIV-1 cases in Sweden based on multiple biomarker estimate of infection times
Jan Albert [1,2], Federica Giardina [3,4], Ethan Romero-Severson , Maria Axelsson , Veronica Svedhem [6,7] Thomas Leitner , Tom Britton 
Affiliates:  Department of Microbiology, Tumor and Cell Biology, Karolinska Institute, Stockholm, Sweden.  Department of Clinical Microbiology, Karolinska University Hospital, Stockholm, Sweden.  Department of Mathematics, Stockholm University, Stockholm, Sweden.  Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, NM.  Public Health Agency of Sweden, Solna, Sweden.  Unit of Infectious diseases, Department of Medicine Huddinge, Karolinska Institute, Stockholm, Sweden.  Department of Infectious Diseases, Karolinska University Hospital, Stockholm, Sweden.
Accurate estimation of time of infection (TI) for persons living with HIV-1 (PLHIV) is important for understanding the epidemiology of HIV and for informing public health decisions. We developed a multiple biomarker method of estimating TI for PLHIV that we use to estimate HIV-1 incidence and proportion of undiagnosed PLHIV in Sweden 2010-2015.
A Bayesian non-linear mixed effects model based on three biomarkers (CD4 counts, BED serology and polymorphisms in HIV-1 pol sequences) was developed to estimate TI in the three main transmission groups: men who have sex with men (MSM), intravenous drug users (IDUs) and heterosexually infected persons (HET). The model was trained on longitudinal data from 31 treatment-naïve patients with well-defined infection times, and subsequently used to estimate TI for 1,357 patients diagnosed in Sweden during 2003-2010. The model was extended to include all patients in Sweden and the time-distribution between arrival in Sweden and diagnosis for immigrants.
The multiple-biomarker model was more accurate than single biomarkers (mean absolute error 1.01 vs ≥ 1.95). We inferred that domestic infections decreased from 280 (95% CI 256-306) in 2010 to 123 (95% CI 105-139) persons (p<0.01) in 2015. Addressing the UNAIDS 90-90-90 target, we estimate that 813 (95% CI 780-862) PLHIV were undiagnosed in 2015, representing a proportion of 10.8% (95% CI 10.4-11.3%) of all PLHIV.
HIV-1 incidence in Sweden was estimated to have decreased and the proportion of diagnosed PLHIV was estimated to be close to the 90% UNAIDS target.