The study had been implemented in 13 cities that are european. The choice to utilize Time Location Sampling (TLS) or Respondent Driven Sampling (RDS) to recruit participants had been according to preliminary research that is formative. TLS (also referred to as Venue evening Sampling, Temporal Spatial Sampling, and Time Venue Sampling) ended up being utilized to recruit individuals in Brussels, Sofia, Hamburg, Warsaw, Lisbon, Ljubljana, Barcelona, Stockholm, and Brighton (letter = 3596). TLS is a quasi method that is probabilistic to recruit users of a target population at particular times in set venues. 17 In this research, the venues or settings for data collection included social and/or commercial venues and cruising settings preliminarily identified through formative research and that have been then chosen arbitrarily for information collection sampling calendars. 18 RDS had been found in Bratislava, Bucharest, Verona, and Vilnius (letter = 1305). RDS is comparable to snowball sampling for the reason that it entails the prospective populace become socially networked so individuals can ask their peers to engage. Nevertheless, RDS is significantly diffent for the reason that it includes many theoretical presumptions to decrease the many biases present in standard snowball sampling methods (see 19 ). Enrolment for RDS in Sialon II had been in line with the individualsвЂ™ social networking and also for the information collection, locally accredited medical facilities ( e.g. a medical center) were used. In TLS towns and cities, individuals had been recruited during 2013, whilst in RDS metropolitan areas recruitment were only available in 2013 and completed in 2014. Ahead of the study we estimated a 50% reaction price included in the test size calculations. an information collection procedure to record refusals had been consequently developed for TLS just.