Some methodological issues in the study of sexual networks - From model todata to model

Background: Mixing between sexual activity classes is an important determin ant of sexually transmitted disease transmission. However. attempts to esti mate sexual mixing patterns in the field remain limited partly because of p ractical and methodological difficulties. Goal: To evaluate and identify appropriate sampling schemes to estimate the mixing pattern between sexual activity classes from large population netwo rks with one or more components. Study Design: The study is based on simulations of large population network s with various structural characteristics. A variety of snowball sampling s chemes are applied to these networks and are evaluated by the quality of th e mixing matrix estimates that they produce. Results and Conclusions: Unbiased estimation of mixing patterns (global ass ortativity, within-group mixing of the lowest activity classes, within-grou p mixing of the highest activity classes) from large population networks is possible with a snowball sampling design in which the initial sample of in dex cases is drawn from the general population, all partners of the index c ase are recruited, and only one generation of partners are traced (one cycl e). Simulation techniques proved useful in addressing complex methodologica l issues in situations where analytic results are difficult to obtain.