Table 2. The result of the critical appraisal for the included studies based on the adapted Newcastle-Ottawa scale.
| Selection | Comparability Max 2* | Outcomes | |||||||
|---|---|---|---|---|---|---|---|---|---|
| No | Study (First Author) | Representativeness of the sample | Sample Size (max 1*) | Non-respondent | Ascertainment of Exposure (max 2*) | Assessment (max 2*) | Statistical Test- confidence interval | Total score | |
| 1 | Abdelrahman, H., et al. (2014) [10] | registry, selection bias unclear | * | probability of missing data high | NA | NA | ** | * | 5 out of 6 |
| 2 | Al-Ghamdi, A. S. (2002). [11] | * | * | * | NA | NA | ** | Not used | 5 out of 6 |
| 3 | Al-Shaqsi, S., et al. (2014). [12] | * | * | * | NA | ** EMS group compared to non-EMS | ** | * | 8 out of 8 |
| 4 | Al-Thani, H., et al. (2014). [13] | * | * | * | NA | ** group intubated by EMS compared to group intubated by ER | ** | * | 8 out of 8 |
| 5 | Alanazi, A. F. (2012). [14] | * | * | did not show total number, missing data unclear | NA | NA | * | Not used | 3 out of 6 |
| 6 | AlHabib, K. F., et al. (2014). [15] | registry, selection bias unclear | * | * | NA | ** compares groups | ** | * | 7 out of 8 |
| 7 | AlHabib, K. F., et al. (2016). [16] | registry, selection bias unclear | * | * | NA | **compares groups | ** | * | 7 out of 8 |
| 8 | AlHabib, K. F., et al. (2019).[17] | registry, selection bias unclear | * | * | NA | ** compares groups | ** | * | 7 out of 8 |
| 9 | Alrazeeni, D. M., et al. (2016). [18] | * | * | * | NA | NA | ** | Not used | 5 out of 6 |
| 10 | Althubaity, E., et al. (2013). [19] | * | * | * | NA | ** compares 3 groups | * | 6 out of 8 | |
| 11 | Batt, A. M., et al. (2016). [20] | * | * | * | NA | NA | ** | * | 6 out of 6 |
| 12 | Bin Salleeh, H. M., et al. (2015). [21] | single center | small sample | * | NA | ** Traumatic OHCA compared to non-traumatic OHCA | ** | * | 6 out of 8 |
| 13 | Callachan, E. L., et al. (2016). [22] | * | * | did not show total number, missing data unclear | NA | NA | ** | * | 5 out of 6 |
| 14 | Callachan, E. L., et al. (2016). [23] | * | * | * | NA | ** EMS group compared toh non-EMS | ** | * | 8 out of 8 |
| 15 | Callachan, E. L., et al. (2017). [24] | selection bias likely | * | did not show total number, missing data unclear | NA | ** | ** | * | 6 out of 8 |
| 16 | Dhaffar, K. O., et al. (2005). [25] | * | * | probability of missing data high | NA | NA | ** | Not used | 4 out of6 |
| 17 | El-Menyar, Ayman., et al (2018) [26] | registry, selection bias unclear | * | * | NA | **compares 2 group | ** | * | 7 out of 8 |
| 18 | Fares, S., et al. (2011). [27] | registry, selection bias unclear | * | * | NA | ** EMS group compared to non-EMS | ** | * | 8 out of 8 |
| 19 | Hamam, A. F., et al. (2015). [28] | * | * | did not show total number, missing data unclear | NA | NA | * | Not used | 3 out of 6 |
| 20 | Irfan, F. B., et al. (2016). [29] | * | * | * | NA | ** compares 2 groups | ** | * | 8 out of 8 |
| 21 | Irfan, F. B., et al. (2017). [30] | * | * | * | NA | ** compares 2 groups | ** | * | 8 out of 8 |
| 22 | Nadar, Sunil K., et al. (2018) [31] | single center | small sample | * | NA | **compares 2 groups | ** | * | 6 out of 8 |
| 23 | Ong, Marcus Eng Hock, et al. (2015) [32] | single center | * | did not show total number, missing data unclear | NA | NA | ** | * | 4 out of 6 |
| 24 | Shehab, A, et al. (2014) [33] | registry, selection bias unclear | * | * | NA | ** compares 2 groups | ** | * | 7 out of 8 |
| 25 | Tham, L. P., et al. (2018). [34] | single center | small sample | did not show total number, missing data unclear | NA | NA | ** | * | 3 out of 6 |
*value equal to one for scoring, EMS: Emergency Medical Services; OHCA: out-of-Hospital cardiac arrest; NA; not applicable