Grading quality of evidence and strength of recommendations for diagnostic tests and strategies - Schunemann, HJ; Oxman, AD; Brozek, J; Glasziou, P; Jaeschke, R; Vist, GE; Williams, JW, Jr.; Kunz, R; Craig, J; Montori, VM; Bossuyt, P; Guyatt, GH; Group GW (BMJ, 2008)