Table 1.

Strategies employed for recruiting participants.

Recruitment strategy	Description
Pilot study	We pilot tested the recruitment protocol in two polling areas in 2012–13 [7]. During the pilot, study packs (invitation letter from the Indian principal investigator, consent form, study information sheet and the schedule of upcoming home visit) were mailed to 160 potential participants (@80 per polling area), at least a week in advance of the scheduled home visit. Due to incorrect home addresses, nearly half of the posted packs were returned or did not reach the intended individuals. Therefore, to locate the households of potential participants, the study team decided to engage trained volunteers from the local community. Additionally, the pilot study showed that in order to achieve a gender balance in the study sample, it is essential to screen more men than women for the following reasons. Compared to women, men were less likely to have IDRS score ≥60 and to attend for the OGTT screening, and more likely to have diabetes on the OGTT. Thus, of the 80 individuals who were selected randomly from each polling area, 50 were men and 30 were women.
Engaging community leaders and local resource persons	We approached the elected representatives (referred as community leaders hereafter) of the 60 polling areas, and requested they identify a community volunteer (referred as local resource persons (LRPs) hereafter) for their polling areas. LRPs were female community health workers, educated up to secondary school or higher, and they have a good rapport with the people in the local community. LRPs were formally recruited to the K-DPP recruitment team. During home visits, LRPs accompanied the field staff and helped them in locating the correct home address of potential participants, gave participants a telephone reminder on the day before their scheduled clinic date and assisted in organizing clinics.
Gender matching of staff	Experience from our previous studies in the study region [[17], [18], [19]] have shown that men are generally less likely to be available at home in the morning hours, owing to work commitments. Therefore, we gender matched our recruitment staff i.e. male staff to contact male participants and female staff to contact female participants, so that male staff could contact male participants during late evening hours after they had return from work.
Follow-up clinics	Participants who were not able to attend clinics in the first instance were invited to attend follow-up clinics. Each follow-up clinic was conducted for participants from two to three neighborhoods within close proximity.