Aurora Kaila (1,2), Inka Aho (1,2), Kirsi Liitsola (3), Eija Hitunen-Back (1,4), Henrikki Brummer-Korvenkontio (3), Jukka Ollgren (3), Pia Kivelä (1,2)

Affiliates

1. Faculty of Medicine, University of Helsinki, Helsinki, Finland. 2. Department of Infectious Diseases, Helsinki University Hospital, Inflammation Center, Helsinki, Finland. 3. Department of Health Security, Finnish Institute for Health and Welfare, Helsinki, Finland. 4. Clinic of Venereal Diseases, Helsinki University Hospital, Inflammation Center, Helsinki, Finland.

Abstract

Background
This retrospective Finnish national register study describes the prevalence and temporal relationship of sexually transmitted infections (STIs), before and after HIV diagnosis. National studies on this topic have not been conducted previously.

Untreated STIs increase the risk for both acquisition and transmission of untreated HIV by various mechanisms, such as genital ulcers and mucosal inflammation. The aim of this study was to identify risk groups to whom preventive measures should be especially targeted to prevent further HIV and STI transmissions.

Methods

We combined two national registers, the Finnish National Infectious Diseases Register (NIDR) and the Finnish HIV Quality of Care Register (FINHIV) to obtain comprehensive national data on all people diagnosed with or being treated for HIV in Finland since 1984 and on their STIs registered since 1995. The follow-up period of this study was from 1995 to 2019.

STIs under assessment were limited to chlamydial infections, gonorrhea, syphilis, hepatitis B, and hepatitis C. Among people who inject drugs (PWIDs) the hepatitises were excluded. Reporting of HIV and these infectious diseases to NIDR is mandatory according to the Finnish legislation. The risk factors for STI acquisition were modelled with Cox model for time dependent variables.

Results
The study comprised 4133 people with HIV (PWH). The majority were of Finnish origin (2444, 60%), male (2943, 71%), from the Helsinki metropolitan area (2434, 59%), and 25-39 years of age at the time of HIV diagnosis (2130, 52%). The transmission mode of HIV was heterosexual in 45%, sex between men in 31%, and injection drug use in 11%.

1213 (29%) were diagnosed with at least one STI. In total they had 2238 STI episodes; 903 (40%) chlamydia, 499 (22%) gonorrhea, 484 (22%) syphilis, 144 (6%) hepatitis B, and 208 (9%) hepatitis C. Of all the STI episodes, 68% were among men having sex with men (MSM). STIs were found in 480 persons during the pre-HIV period, 860 during the post-HIV period and 366 both pre- and post-HIV periods.

The incidence of any STI was 28/1000py (95% CI: 26-30) before HIV diagnosis and 30/1000py (95% CI: 28-32) after HIV diagnosis. The STI incidence increased over time, more pronounced among MSM. In the Cox model, age was used as a baseline hazard. The predicted hazard ratios for different modes of transmission before and after HIV diagnosis are shown in figure 1.

Conclusions
The majority (70%) of all PWH had no STIs. The overall STI incidence after HIV diagnosis appeared slightly higher than before the diagnosis. However, the incidence of STIs increased over time. The model including time dependent variables showed that predicted hazard for STIs after HIV diagnosis was equal or lower than before HIV diagnosis, regardless of HIV transmission mode. Of note, the results may be at least partly affected by increased diagnostics after HIV diagnosis. The relatively frequent STIs before HIV diagnosis present an opportunity for HIV prevention or early diagnosis. After HIV diagnosis, low threshold STI testing should be offered for patients, especially for those with earlier STI history.