Developing consensus measures for global programs: lessons from the Global Alliance for Chronic Diseases Hypertension research program von Riddell, MA, Edwards, N, Thompson, SR, Bernabe-Ortiz, A, Praveen, D, Johnson, C, Kengne, AP, Liu, P, McCready, T, Ng, E, Nieuwlaat, R, Ovbiagele, B, Owolabi, M, Peiris, D, Thrift, AG, Tobe, S, Yusoff, K, GACD Hypertension Research Programme