The Newcastle-Ottawa Scale (NOS) for assessing the quality of included studies
| Selection | Representativeness of the exposed cohort | This item will be assigned a ‘⋆’ when all eligible patients with LC are included in analysis during study period |
| Selection of the non-exposed cohort | This item will be assigned a ‘⋆'when all eligible patients with non-LC are included in analysis during study period | |
| Ascertainment of exposure | This item will be assigned a ‘⋆'when lactate is directly obtained from medical chart, not by reporting from the patient | |
| Outcome of interest is not present at the start of study | This item will be assigned a ‘⋆’ when death is not occurred within the time frame for determining LC | |
| Comparability | Comparability of cohorts on the basis of design or analysis | Baseline characteristics of LC and non-LC patients are comparable. Usually this can be found in table 1 |
| Outcome | Assessment of outcome | This item will be assigned a ‘⋆’ when mortality is assessed by investigator, not by the report of the patient's family or next-of-kin. |
| Is follow-up long enough for outcome to occur | The adequate follow-up is during hospital stay | |
| Adequacy of follow-up of cohort | This item will be assigned a ‘⋆’ when follow-up rate >95% |
LC, lactate clearance.