“…Diaries have been used to register participants’ symptoms in studies of gastrointestinal and respiratory illness, including randomized controlled trials in which illness is defined according to clinical symptoms (Blanken et al, 2013; Martin, Fairchok, Stednick, Kuypers, & Englund, 2013; Pappas, Hendley, Hayden, & Winther, 2008). The use of symptom diaries has been validated in various settings (Stanton et al, 1987; Watson, Little, Moore, Warner, & Williamson, 2001), and previous studies indicate that pictorial diaries validly capture incidence of morbidity in low- and middle-income countries (Goldman, Vaughan, & Pebley, 1998; Wright et al, 2006).…”