“…Thirty-five studies reported on referral rates [3,7,; 28 of these were observational studies [3,7,[12][13][14][16][17][18][19][20][21][22][23][25][26][27][28][29][30][31][34][35][36][37][40][41][42]44], while the remaining seven assessed the effect of an intervention on COPD care (and measured referral rates at baseline and post-intervention) [15,24,32,33,38,39,43]. Nine studies reported on HCP perceived barriers to PR referral [23,26,[45][46][47][48][49][50][51], and seven of these also reported on enablers [23,26,45,…”