P18.05 Contribution of biomarkers to the validation of self-reported condom use in a treatment as prevention and a pre-exposure prophylaxis demonstration study among female sex workers
Bibliographic record
Abstract
Introduction The phenomenon of condom migration remains a major concern whenever a new HIV prevention approach is being considered to strengthen the existing preventive arsenal. We are currently measuring the baseline condom use at the recruitment visit of an on-going demonstration study on pre-exposure prophylaxis (PrEP) and treatment as prevention (TasP), involving female sex workers (FSWs) in Cotonou, Benin, West Africa. Methods During the recruitment visit, data on unprotected sex were collected through face-to-face interviews, from the first 112 FSWs with available biomarker results, recruited as of February 28, 2015. In addition, vaginal samples were tested for prostate-specific antigen (PSA) and Y chromosome DNA (Yc-DNA) PCR tests, to validate the self-reported unprotected sex. Additional biomarkers include gonorrhoea and chlamydia testing using nucleic-acid amplification tests and urine pregnancy tests. Performance parameters of the self-reported unprotected sex were calculated using combined results of all biomarkers as gold standard for recent semen exposure. Results The prevalence of recent self-reported unprotected sex with all types of sexual partners was 31.2% (35/112) vs. 51.8% (58/112) according to the combined biomarkers (p = 0.003, McNemar test). Using the combined biomarkers as gold standard, the sensitivity and specificity of self-reported unprotected sex were 34.5% and 72.2%, respectively. The prevalences of gonorrhoea and chlamydia at the recruitment visit were 8.0% (9/112) and 6.2% (7/112), respectively. Either infection was present in 16 participants (14.3%), out of whom 10 were positive for PSA or Yc-DNA PCR. The pregnancy test was positive for two participants of whom one was positive for both PSA and Yc-DNA PCR. Conclusion These results confirm the questionable validity of self-reported condom use among FSWs. They underscore the need of supplementing self-reported data by biomarkers to improve data reliability. These early results are part of the baseline data that will be subsequently used to look for condom migration. Disclosure of interest statement This study is funded by the Bill and Melinda Gates Foundation, and Truvada® for pre-exposure prophylaxis is provided free of charge by Gilead Sciences, Inc.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.011 | 0.035 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.002 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.007 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".