Who is sexually active? Using a multicomponent sexual activity profile (MSAP) to explore, identify and describe sexuallyactive high-school students in rural KwaZulu-Natal, South Africa

: Understanding sexual activity is necessary to prevent sexually transmitted infections. Evidence from Sub-Saharan Africa suggests that 10–20% of youth aged 15–24 are sexually active before reaching 15 years, yet estimating sexual activity remains challenging. This study explored the use of multiple sexual health outcomes to identify sexually-active young women in rural KwaZulu-Natal, South Africa. Methods: Using a multi-component sexual activity profile (MSAP), we aimed to identify sexually active students. Based on data from 2675 grade 9 and 10 students attending 14 high schools) in rural KwaZulu-Natal, we constructed a descriptive diagram identifying students who were sexually active by self-report vs MSAP profile. T-tests for two independent samples was performed to compare by sex and ecological variables that characterise students newlyidentified as sexually active. Results: Using self-report only, 40.3% self-reported as sexually active, whilst the MSAP identified 48.7% (223 additional students). More females were identified than males. Younger adolescents were more likely to underreport sexual activity but were identified using MSAP. Newly-identified as sexually active were more likely to be female (p = < 0.000), 15 years old or younger (p = 0.008), less likely to perceive being at risk (p = 0.037) or have ever used alcohol (p = < 0.000). At a relational level, they were less likely to report having ever had a boyfriend/girlfriend (p = 0.000) or to have felt pressured to have sex by their peers (p = < 0.000) or partners (p = 0.008). At a familial level they more likely to be of medium socioeconomic (SES) status (p = 0.037) whilst at a school and community level they were less likely to have repeated a grade (p = 0.024) and were more likely to be engaged in social activities (p = 0.032)