“…Previous publications have provided mixed opinions on whether quality scoring should be used as a weighting variable. Some articles comment that quality scoring adds subjective bias and may lack validity, and results may not represent quality (Bonovas, Filioussi, & Sitaras, 2006;Greenland, 1994;Juni, Witschi, Bloch, & Egger, 1999;Stroup et al, 2000). Other studies claim that quality scoring can be done but recommend not using the scores as weights but rather using the summary score as a covariate to conduct subgroup and sensitivity analysis (Berman & Parker, 2002;Friedenreich, Brant, & Riboli, 1994;Stroup et al, 2000).…”