Prevalence and risk factors associated with HIV and syphilis co-infection in the African Cohort Study: a cross-sectional study
Authors: Gilbert Laura , Dear Nicole , Esber Allahna , Iroezindu Michael , Bahemana Emmanuel , Kibuuka Hannah , Owuoth John , Maswai Jonah , Crowell Trevor A. , Polyak Christina S. , Ake Julie A. ,   the AFRICOS Study Group, Bartolanzo Danielle , Reynolds Alexus , Song Katherine , Milazzo Mark , Francisco Leilani , Mankiewicz Shauna , Schech Steven , Golway Alexandra , Omar Badryah , Mebrahtu Tsedal , Lee Elizabeth , Bohince Kimberly , Parikh Ajay , Hern Jaclyn , Duff Emma , Lombardi Kara , Imbach Michelle , Eller Leigh Anne , Kibuuka Hannah , Semwogerere Michael , Naluyima Prossy , Zziwa Godfrey , Tindikahwa Allan , Mutebe Hilda , Kafeero Cate , Baghendaghe Enos , Lwebuge William , Ssentogo Freddie , Birungi Hellen , Tegamanyi Josephine , Wangiri Paul , Nabanoba Christine , Namulondo Phiona , Tumusiime Richard , Musingye Ezra , Nanteza Christina , Wandege Joseph , Waiswa Michael , Najjuma Evelyn , Maggaga Olive , Kenoly Isaac Kato , Mukanza Barbara , Maswai Jonah , Langat Rither , Ngeno Aaron , Korir Lucy , Langat Raphael , Opiyo Francis , Kasembeli Alex , Ochieng Christopher , Towett Japhet , Kimetto Jane , Omondi Brighton , Leelgo Mary , Obonyo Michael , Rotich Linner , Tonui Enock , Chelangat Ella , Kapkiai Joan , Wangare Salome , Kesi Zeddy Bett , Ngeno Janet , Langat Edwin , Labosso Kennedy , Rotich Joshua , Cheruiyot Leonard , Changwony Enock , Bii Mike , Chumba Ezekiel , Ontango Susan , Gitonga Danson , Kiprotich Samuel , Ngtech Bornes , Engoke Grace , Metet Irene , Airo Alice , Kiptoo Ignatius , Owuoth John , Sing’oei Valentine , Rehema Winne , Otieno Solomon , Ogari Celine , Modi Elkanah , Adimo Oscar , Okwaro Charles , Lando Christine , Onyango Margaret , Aoko Iddah , Obambo Kennedy , Meyo Joseph , Suja George , Iroezindu Michael , Adamu Yakubu , Azuakola Nnamdi , Asuquo Mfreke , Tiamiyu Abdulwasiu Bolaji , Kokogho Afoke , Mohammed Samirah Sani , Okoye Ifeanyi , Odeyemi Sunday , Suleiman Aminu , Umejo Lawrence , Enas Onome , Mbachu Miriam , Chigbu-Ukaegbu Ijeoma , Adai Wilson , Odo Felicia Anayochukwu , Abdu Rabi , Akiga Rosemary , Nwandu Helen , Okolo CHisara , Okeke Ndubuisis , Parker Zahra , Linus Asogwa Ugochukwu , Agbaim Concilia Amaka , Adegbite Tunde , Harrison Nkenchiere , Adelakun Adewale , Chioma Ekeocha , Idi Victoria , Eluwa Rachel , Nwalozie Jumoke , Faith Igiri , Okanigbuan Blessing , Emmanuel Achugwo , Nnadi Nkiru , Rosemary Ndubuisi , Natalie Uzoegwu Amaka , Owanza Obende Theresa , Francis Falaju Idowu , Elemere Jacintal , Lauretta Obilor Ifeoma , Akinwale Edward , Ochai Inalegwu , Maganga Lucas , Bahemana Emmanuel , Khamadi Samoel , Njegite John , Lueer Connie , Kisinda Abisai , Mwamwaja Jaquiline , Mbwayu Faraja , David Gloria , Mwaipopo Mtasi , Gervas Reginald , Mkondoo Doroth , Somi Nancy , Kiliba Paschal , Mwaisanga Gwamaka , Msigwa Johnisius , Mfumbulwa Hawa , Edwin Peter , Olomi Willyhelmina 
Published: October 2021

Abstract
Background
Each year, 5.6 million new syphilis cases are diagnosed globally. Guidelines for people living with HIV (PLWH) in low-income countries (LIC) recommend STI testing for symptomatic persons and those newly diagnosed with HIV; routine STI testing is less clear. Here we provide updated syphilis prevalence and identify co-infection risk factors in PLWH in the African Cohort Study (AFRICOS) to understand these rates as they relate to syndromic treatment.

Methods
AFRICOS is a study enrolling PLWH and HIV-uninfected individuals in four African countries. Participant study enrollment information was used to determine syphilis prevalence and co-infection risk factors. Inclusion criteria consisted of adults 18 years or older receiving care at a participating clinic as a long-term resident who consented to data and specimen collection. Exclusion criteria consisted of pregnancy and/or imprisonment. Screen-positive syphilis was defined as a reactive rapid plasma regain (RPR) upon study enrollment whereas confirmed syphilis included a reactive RPR followed by reactive treponemal test. Multivariate analyses was performed to determine HIV and syphilis co-infection risk factors.

Results
Between 2013 and March 1, 2020, 2939 PLWH enrolled and 2818 were included for analysis. Screen-positive and confirmed syphilis prevalence were 5.3% (151/2818) and 3.1% (87/2818), respectively. When the analysis was restricted to PLWH with an RPR titer of greater than, or equal to, 1:8, 11/87 (12.6%) participants were included. No PLWH and confirmed syphilis had documented genital ulcers. In the multivariate model, participants with confirmed syphilis co-infection were more likely to have none or some primary education [aOR 3.29 (1.60, 6.74)] and consume alcohol [aOR 1.87 (1.16, 3.03)] compared to those without syphilis. Antiretroviral therapy (ART) with suppressed viral load (VL) was protective in the unadjusted model but not adjusted multivariate model.

Conclusions
Our findings show that syphilis rates in sub-Saharan Africa remain elevated where diagnosis remains challenging, and that both lower education level and alcohol consumption are significantly associated with HIV/syphilis co-infection in AFRICOS. Based on our analysis, current STI guidelines targeting testing for African individuals with either new HIV diagnosis or syndromic symptoms may be inadequate, highlighting the need for increased testing and treatment strategies in resource-limited settings.