Factors affecting heterogeneity
| Factor (No. of Studies) | τ2 | χ2 (P) | I2 (%) | Mean Differences (95 % CI) Random |
|---|---|---|---|---|
| Studies without significant differences between grades II and III (n = 14) | 0.00 | 6.5 (.84) | 0 | 0.35 (0.01–0.69) |
| Oligodendroglial tumors (n = 3) | 0.04 | 2.17 (.34) | 8 | 1.95 (1.21–2.96) |
| Histogram rCBVmax (n = 3) | 0.10 | 2.88 (.24) | 31 | 0.45 (−0.17–1.08) |
| Published individual patient data (n = 10) | 0.28 | 15.76 (<.001) | 43 | 1.82 (1.28–2.36) |
| Retrospective study design (n = 17) | 0.70 | 52.34 (<.001) | 69 | 1.42 (0.89–1.96) |
| Astrocytic tumors (n = 6) | 1.57 | 20.69 (<.001) | 76 | 2.28 (0.96–3.60) |
| Studies with significant differences between grades II and III (n = 16) | 0.73 | 63.01 (<.001) | 76 | 2.37 (1.87–2.87) |
| Non-WHO 2007 classification (n = 17) | 0.88 | 73.74 (<.001) | 78 | 1.71 (1.16–2.26) |
| No correction for contrast agent leakage according to Boxerman (n = 20) | 0.88 | 86.07 (<.001) | 78 | 1.75 (1.24–2.25) |
| ROI analysis (n = 25) | 1.09 | 116.10 (<.001) | 79 | 1.93 (1.43–2.44) |
| Studies published in 2010 or before (n = 14) | 1.02 | 65.67 (<.001) | 80 | 1.81 (1.17–2.44) |
| No presaturation of tissue (n = 18) | 1.05 | 84.70 (<.001) | 80 | 1.85 (1.27–2.43) |
| All studies (n = 28) | 1.16 | 142.97 (<.001) | 81 | 1.76 (1.27–2.24) |
| 3T (n = 10) | 1.67 | 46.71 (<.001) | 81 | 1.66 (0.69–2.64) |
| Presaturation of tissue (n = 10) | 1.53 | 53.21 (<.001) | 83 | 1.60 (0.68–2.15) |
| Studies published after 2010 (n = 14) | 1.50 | 75.04 (<.001) | 83 | 1.70 (0.93–2.48) |
| 1.5T (n = 16) | 1.17 | 95.95 (<.001) | 84 | 1.83 (1.22–2.45) |
| WHO 2007 classification (n = 11) | 2.07 | 68.39 (<.001) | 85 | 1.85 (0.85–2.86) |
| No published individual patient data (n = 18) | 1.54 | 120.79 (.07) | 86 | 1.75 (1.07–2.42) |
| Blinded reference test evaluation (n = 5) QUADAS-2 | 1.10 | 29.23 (<.001) | 86 | 1.30 (0.29–2.32) |
| Correction for leakage according to Boxerman (n = 8) | 2.58 | 54.12 (<.001) | 87 | 1.83 (0.49–3.16) |
| Blinded index test evaluation (n = 14) QUADAS-2 | 1.57 | 97.79 (<.001) | 87 | 1.77 (1.03–2.51) |
| Optimal flow and timing (n = 7) QUADAS-2 | 1.57 | 49.31 (<.001) | 88 | 1.69 (0.57–2.80) |
| Prospective study design (n = 11) | 1.94 | 89.9 (<.001) | 89 | 2.27 (1.35–3.20) |