Table 2.
Methodological information for dealing with zero-events studies
| Methodological information for dealing with zero-events studies | Yes (%, exact CI) | No (%, exact CI) | NC or NA (%, exact CI) | Total |
|---|---|---|---|---|
| 1) In the systematic review, did any meta-analysis contain zero-events studies? | 406 (63.44, 59.57 to 67.18) | 88 (13.75, 11.18 to 16.66) | 146 (22.81, 19.62 to 26.26) | 640 |
| 2) If zero-events studies were involved, what were the types of zero-events studies? | 406 | |||
| • Single-arm-zero-events only | 174 (42.86, 37.99 to 47.83) | ‐ | ‐ | |
| • Double-arm-zero-events only | 7 (1.72, 0.70 to 3.52) | ‐ | ‐ | |
| • Both single and double | 208 (51.23, 46.25 to 56.19) | ‐ | ‐ | |
| • At least containing single-arm-zero-events study | 7 (1.72, 0.70 to 3.52) | ‐ | ‐ | |
| • At least containing double-arm-zero-events study | 8 (1.97, 0.85 to 3.85) | ‐ | ‐ | |
| • Cannot be judged | 2 (0.49, 0.06 to 1.77) | ‐ | ‐ | |
| 3) If zero-events studies were involved, whether the authors specified methods to deal with zero-events studies? | 131 (32.27, 27.74 to 37.05) | 275 (67.73, 62.95 to 72.26) | 0 (0.00, 0.00 to 0.90) | 406 |
| 4) If the authors specified methods, whether they clarified reasons for selecting the method for zero-events studies? | 44 (33.59, 25.58 to 42.36) | 87 (66.41, 57.64 to 74.42) | 0 (0.00, 0.00 to 2.78) | 131 |
| 5) If zero-events studies were involved, how zero-events studies were dealt with by the authors? | See detailed methods in Fig. 2 | |||
| • Discarding single-arm-zero-events studies (174 + 208 + 7 = 389) | 3 (0.77, 0.16 to 2.24) | 384 (98.71, 97.03 to 99.58) | 2 (0.51, 0.06 to 1.85) | 389 |
| • Discarding double-arm-zero-events studies (7 + 208 + 8 = 223) | 170 (76.23, 70.09 to 81.66) | 50 (22.42, 17.12 to 28.47) | 3 (1.35, 0.28 to 3.85) | 223 |
| 6) Whether a sensitivity analysis was employed through at least one different synthesis method for dealing with zero-events studies? | 53 (13.05, 9.93 to 16.73) | 353 (86.95, 83.27 to 90.07) | 0 (0.00, 0.00 to 0.90) | 406 |
| 7) For those failed to synthesize studies with zero-events, did the authors discuss about the potential impact of such studies (e.g., discarding them) on the results? | 22 (12.94, 8.29 to 18.94) | 148 (87.06, 81.06 to 91.71) | 0 (0.00, 0.00 to 2.15) | 170 |
NC not clear; NA not applicable