Sample populations

Subjects in Seattle, WA, USA were recruited via flyers and emails that were posted and sent throughout the University of Washington campus. Samples were collected from subjects in their workplaces. Samples were stored at -80°C within 8 hours of collection, and subsequently tested by qPCR as described below.

Samples archived as part of a previous study on the use of oral swabs in the diagnosis of adult pulmonary TB patients in South Africa [1] were also used for the current study. South African participants had been recruited in clinics in Worcester, Western Cape (population 350,000). As described previously, these samples were collected from subjects in clinics or homes, stored at -80°C within 8 hours of collection, and shipped frozen to Seattle where they were assayed by qPCR for M. tuberculosis DNA [1]. For the current study these archived samples were screened for human mtDNA.

Protocols for collecting samples from U.S. subjects were approved by the University of Washington’s Human Subjects Division. Archived South African samples collected for the previous study focusing on TB diagnosis [1] were used in the current study under “future use” provisions in consent forms, as approved by the University of Washington and the University of Cape Town.