Comparison of Self-Reported Sexual Activity Among Heterosexuals with Sexual Spread of Poorly Transmittable Agents: A Minimalistic Approach to Estimating Sexual Activity Based on HIV Incidence

Modelling of doxycycline-based prevention of bacterial sexually transmitted infections in comparison to condom-based and test-based prevention

Background

Doxycycline-based prevention of bacterial sexually transmitted infections (STIs) has been assessed in various studies and has been recommended by the European AIDS Clinical Society to be proposed to persons with repeated STIs on a case-by-case basis. However, while good preventive effects could be shown for Chlamydia trachomatis and Treponema pallidum in Europe, no reliable prevention against doxycycline resistance-affected bacterial causes of STIs like Neisseria gonorrhoeae and Mycoplasma genitalium was confirmed.

Methods

In a modelling-approach, we assessed potential beneficial effects even against the latter microorganisms in case of optimized adherence with doxycycline prevention. These effects were modelled for Germany in comparison to traditional prevention schemes like condom-based STI-prevention and testing-as-prevention.

Results

With estimated risk reduction in the ranges of 86% for N. gonorrhoeae and of 82% for Mycoplasma genitalium, expectable preventive efficacy similar to alternative preventive approaches could be calculated in case of optimized adherence with doxycycline prevention. In case of repeated risk exposure, the preventive potential of condom-based prevention was decreased compared to both optimized doxycycline prevention and testing-as-prevention.

Conclusions

As suggested by the applied modelling, the preventive effect of optimized doxycycline prevention against bacterial STIs is in a similar range, like other common prevention strategies.

Optimization of Case Definitions for Sensitivity as a Preventive Strategy-A Modelling Exemplified with Rapid Diagnostic Test-Based Prevention of Sexual HIV Transmission

In clinical studies, case definitions are usually designed to optimally match the desired clinical state, because lacking specificity is associated with a risk of bias regarding the study outcome. In preventive medicine, however, high sensitivity is sometimes considered as more critical in order not to overlook infectious individuals, because the latter may be associated with ongoing spread of a transmittable disease. Accordingly, this work was focused on a theoretical model on how the sensitivity of case definitions can be optimized by adding clinical symptoms to diagnostic results for preventive purposes, if the associated reduction in specificity is considered as acceptable. The model was exemplified with an analysis on whether and in how far exposure risk can be reduced by the inclusion of observable symptoms during seroconversion syndrome in case of rapid diagnostic test-based prevention of sexual HIV transmission. The approach provided a high level of safety (negative predictive values close to 1) for the price of a considerably number of false positives (positive predictive values < 0.01 for some subpopulations). When applying such a sensitivity-optimized screening as a "diagnostics as prevention" strategy, the advantages of excellent negative predictive values need to be cautiously balanced against potential undesirable consequences of low positive predictive values.

Evaluation of the Xiamen AmonMed Biotechnology rapid diagnostic test COVID-19 IgM/IgG test kit (Colloidal gold)

Introduction

To efficiently monitor the COVID-19 pandemic for surveillance purposes, reliable serological rapid diagnostic tests (RDTs) are desirable for settings where well-established high-throughput bench-top solutions are not available. Here, we have evaluated such an RDT.

Methods

We have assessed the Xiamen AmonMed Biotechnology COVID-19 IgM/IgG test kit (Colloidal gold) and the EUROIMMUN benchtop assay with serum samples from patients with polymerase chain reaction (PCR)-confirmed COVID-19 disease. Samples from patients with Epstein-Barr-virus (EBV) infection and blood donors were used for specificity testing.

Results

For the colloid gold rapid test and the EUROIMMUN assay, the study indicated overall sensitivity of 15.2% and 67.4%, respectively, while specificity of 99.0% and 97.9% with the blood donor sera, as well as 100% and 96.8% with the EBV-patients, were observed, respectively. An association of the time period between positive PCR results and serum acquisition with serological test positivity could be observed for the immunologlobulin G subclass of the EUROIMMUN assay only.

Conclusions

In spite of acceptable specificity of the assessed RDT, the detected poor sensitivity leaves room for improvement. The test results remain difficult to interpret and therefore the RDT can currently not be recommended for routine diagnostic or surveillance use.