Table 1.
Baseline characteristics of the investigative studies reporting blood levels of IL-6 and IL-10 in COVID-19 patients.2,4-7,9-18,24-154.
| Study (reference) | Ethnicity | Location | Setting | Design | No. of participants | Age (mean ± SD) | Disease severity | Mortality | Cytokine assay | Biomarker study | NOS rating |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Bergantini et al 2 | Caucasian | Italy | HB | Monocentric retrospective | 24 | Mild: 62.2 ± 15.6Severe: 65.2 ± 8 | Mild: 14Severe: 10 | NA | ECLIA | IL-6 | 7 |
| Burian et al 24 | Caucasian | Germany | HB | Retrospective cohort | 37 | 61.5 ± 17 | Mild: 25Severe: 12 | NA | Biochemical assay | IL-6 | 7 |
| Cai et al 25 | Asian | China | HB | Retrospective | 298 | 47.17 ± 20.86 | Mild: 240Severe: 58 | NA | Biochemical assay | IL-6 | 8 |
| Chang et al 26 | Asian | China | HB | Retrospective | 150 | NA | Mild: 93Severe: 57 | NA | Biochemical assay | IL-6 | 8 |
| Chen et al 4 | Asian | China | HB | Retrospective cohort | 660 | 52.33 ± 25.26 | NA | Dead: 82Survivors: 578 | Biochemical assay | IL-6 | 8 |
| Chen et al 27 | Asian | China | HB | Retrospective | 21 | 57 ± 11.93 | Mild: 10Severe: 11 | NA | CLIA | IL-6, IL-10 | 8 |
| Chen et al 28 | Asian | China | HB | Retrospective | 172 | 64 | NA | Dead: 87Survivors: 85 | Biochemical assay | IL-6 | 7 |
| Chen et al 29 | Asian | China | HB | Retrospective | 29 | NA | Mild: 15Severe: 14 | NA | ELISA | IL-6, IL-10 | 8 |
| Chen et al 30 | Asian | China | HB | Retrospective observational | 94 | 52.75 ± 16.09 | Mild: 69Severe: 25 | NA | CLIA | IL-6, IL-10 | 9 |
| Chen et al 31 | Asian | China | HB | Retrospective cohort | 548 | 56 ± 14.5 | Mild: 345Severe: 203 | Dead: 103Survivors: 445 | Biochemical assay | IL-6 | 8 |
| Chen et al 5 | Asian | China | HB | Retrospective cohort | 274 | 58.67 ± 19.38 | NA | Dead: 113Survivors: 161 | Biochemical assay | IL-6, IL-10 | 7 |
| Chen et al 32 | Asian | China | HB | Retrospective | 55 | 55 ± 54.05 | NA | Dead: 19Survivors: 36 | Biochemical assay | IL-6 | 6 |
| Chen et al 9 | Asian | China | HB | Retrospective | 48 | 64.6 ± 18.1 | Mild: 21Severe: 27 | NA | Biochemical assay | IL-6 | 6 |
| Chen et al 11 | Asian | China | HB | Retrospective | 1453 | NA | Mild: 962Severe: 491 | NA | ELISA | IL-6 | 8 |
| Chi et al 10 | Asian | China | HB | Retrospective cohort | 70 | Mild : 42 ± 10.98Severe: 43.24 ± 14.76 | Mild: 4Severe: 66 | NA | Multiplex biometric immunoassay | IL-6, IL-10 | 8 |
| Crespo et al 33 | Caucasian | Spain | HB | Prospective cohort | 16 | 73.6 ± 4.7 | NA | Dead: 8Survivors: 8 | Biochemical assay | IL-6 | 6 |
| De La Flor et al 34 | Caucasian | Spain | HB | Observational retrospective | 10 | 73.5 ± 9.46 | NA | Dead: 3Survivors: 7 | OLHDF | IL-6 | 7 |
| D’Alto et al 35 | Caucasian | Italy | HB | Prospective | 94 | Dead: 68 ± 12Survivors: 62 ± 13 | NA | Dead: 25Survivors: 69 | Biochemical assay | IL-6 | 7 |
| Ding et al 6 | Asian | China | HB | Prognostic | 104 | 62.82 ± 14.77 | Mild: 50Severe: 54 | Dead: 16Survivors: 88 | Biochemical assay | IL-6 | 7 |
| Ding et al 36 | Asian | China | HB | Retrospective | 32 | Mild: 54.9 ± 11.3Severe: 61.3 ± 17.9Critical: 73.5 ± 12.3 | Mild: 11Severe: 21 | NA | CLIA | IL-6 | 8 |
| El-Shabrawy et al 14 | African | Egypt | HB | Prognostic cohort | 116 | Mild : 44.67 ± 42.13Severe: 54.17 ± 54.97 | Mild: 99Severe: 17 | NA | ELISA | IL-6 | 8 |
| Fan et al 37 | Asian | China | HB | Retrospective | 73 | 58.36 ± 14.31 | NA | Dead: 47Survivors: 26 | Biochemical assay | IL-6 | 7 |
| Fan et al 38 | Asian | China | HB | Retrospective observational | 101 | 65.46 ± 9.74 | NA | Dead: 101Survivors: 0 | Biochemical assay | IL-6 | 8 |
| Fan et al 39 | Asian | China | HB | Retrospective longitudinal | 21 | 62.5 ± 12.6 | NA | Dead: 4Survivors: 17 | Biochemical assay | IL-6 | 6 |
| Fei et al 40 | Asian | China | HB | Retrospective | 72 | Mild: 55.7 ± 11.9Severe: 64 ± 16.8 | Mild: 52Severe: 20 | NA | ELISA | IL-6 | 7 |
| Fei et al 41 | Asian | China | HB | Retrospective cohort | 191 | 56.33 ± 15.69 | NA | Dead: 54Survivors: 137 | Biochemical assay | IL-6 | 7 |
| Feng et al 7 | Asian | China | HB | Single-centered, prospective, and observational | 114 | 63.96 ± 13.41 | Mild: 94Severe: 20 | NA | Biomarkers assay | IL-6, IL-10 | 7 |
| Gadotti et al 12 | Caucasian | Brazil | HB | Prospective cohort | 56 | 60.33 ± 19.78 | NA | Dead: 18Survivors: 38 | ELISA | IL-6, IL-10 | 8 |
| Gan et al 42 | Asian | China | HB | Retrospective case-control | 95 | 65.67 ± 15.06 | NA | Dead: 39Survivors: 56 | Biochemical assay | IL-6, IL-10 | 7 |
| Gao et al 43 | Asian | China | HB | Retrospective | 43 | 43.74 ± 12.12 | Mild: 28Severe: 15 | NA | ECLIA | IL-6 | 8 |
| Gil-Etayo et al 44 | Caucasian | Spain | HB | Prospective observational | 34 | 58.08 ± 23.79 | NA | Dead: 6Survivors: 28 | Flow cytometry | IL-6 | 8 |
| Guirao et al 15 | Caucasian | Spain | HB | Retrospective cohort | 50 | Mild: 56.2 ± 2.85Moderate: 65.7 ± 2.05Severe: 64.5 ± 2.26 | Mild: 10Severe: 40 | Dead: 14Survivor s: 36 | ECLIA | IL-6 | 9 |
| Guner et al 45 | Caucasian | Turkey | HB | Retrospective cohort | 222 | 50.6 ± 16.5 | Mild: 172Severe: 50 | NA | Biochemical assay | IL-6 | 8 |
| Han et al 13 | Asian | China | HB | Retrospective cohort | 102 | Mild: 58.3 ± 12.6Severe: 59.3 ± 14.4Critical:65.1 ± 14.4 | Mild: 42Severe: 60 | NA | Flow cytometry | IL-6, IL-10 | 9 |
| Yang et al 46 | Asian | China | HB | Single-centered, retrospective, and observational | 94 | Dead: 75.8 ± 12.9Survivors: 65.8 ± 10.2 | NA | Dead: 13Survivors: 81 | Biochemical assay | IL-6, IL-10 | 9 |
| Henry et al 18 | Caucasian | USA | HB | Prospective observational | 52 | 52 ± 20.59 | Mild: 36Severe: 16 | NA | ELISA | IL-6, IL-10 | 9 |
| He et al 47 | Asian | China | HB | Retrospective | 204 | 48.33 ± 20.91 | Mild: 135Severe: 69 | NA | Biochemical assay | IL-6, IL-10 | 7 |
| He et al 48 | Asian | China | HB | Single-center retrospective | 93 | 47.9 ± 13.2 | Mild: 60Severe: 33 | NA | Biochemical assay | IL-6, IL-10 | 7 |
| Herold et al 16 | Caucasian | UK | HB | Prospective cohort | 89 | 54.33 ± 49.74 | Mild: 57Severe: 32 | NA | ELISA | IL-6 | 8 |
| Holt et al 49 | Caucasian | USA | HB | Retrospective cohort | 62 | Dead: 74.16 ± 11.4Survivors: 60.3 ± 12.5 | NA | Dead: 19Survivors: 43 | Biochemical assay | IL-6 | 6 |
| Hu et al 50 | Asian | China | HB | Retrospective cohort | 76 | 50.47 ± 3.10 | Mild: 63Severe: 13 | NA | Multiplex biometric immunoassay | IL-6 | 6 |
| Huang et al 51 | Asian | China | HB | Retrospective | 64 | 47.8 ± 18.5 | Mild: 43Severe: 21 | Dead: 4Survivors: 27 | Biochemical assay | IL-6, IL-10 | 6 |
| Huang et al 52 | Asian | China | HB | Single-center retrospective | 218 | 62.33 ± 13.43 | Mild: 116Severe: 102 | NA | ELISA, CLIA | IL-6 | 7 |
| Huang et al 53 | Asian | China | HB | Retrospective | 83 | 62 ± 12.31 | Mild: 21Severe: 62 | NA | Biochemical assay | IL-6 | 6 |
| Jain et al 54 | Asian | India | HB | Prospective observational | 154 | Mild: 42.34 ± 6.41Severe: 51.41 ± 9.12 | Mild: 91Severe: 63 | NA | ELISA | IL-6 | 7 |
| Ke et al 55 | Asian | China | HB | Single-centered, retrospective case-control | 194 | 63.08 ± 12.88 | NA | Dead: 46Survivors: 148 | Flow cytometry | IL-6, IL-10 | 7 |
| Keske et al 56 | Caucasian | Turkey | HB | Retrospective | 43 | 61.67 ± 51.39 | NA | Dead: 6Survivors: 37 | Biochemical assay | IL-6 | 6 |
| Kumar et al 57 | Asian | India | HB | Clinical study | 386 | Dead: 63.4 ± 14Survivors: 48.1 ± 16.3 | NA | Dead: 16Survivors: 370 | CLIA | IL-6 | 8 |
| Laguna-Goya et al 58 | Caucasian | Spain | HB | Prospective cohort | 454 | 52 ± 11.9 | NA | Dead: 33Survivors: 421 | Flow cytometry | IL-6 | 9 |
| Li et al 59 | Asian | China | HB | Retrospective | 476 | 61.33 ± 14.09 | NA | Dead: 183Survivors: 293 | Biochemical assay | IL-6, IL-10 | 7 |
| Li et al 60 | Asian | China | HB | Retrospective cohort | 102 | 57.33 ± 18.8 | NA | Dead: 15Survivors: 87 | Biochemical assay | IL-6, IL-10 | 6 |
| Li et al 61 | Asian | China | HB | Retrospective | 1449 | 55 ± 17.81 | NA | Dead: 122Survivors: 1327 | Biochemical assay | IL-6, IL-10 | 6 |
| Li et al 62 | Asian | China | HB | Single-center, retrospective | 215 | Mild: 42.67 ± 14.96Severe: 49.5 ± 39.57 | Mild: 159Severe: 56 | NA | Flow cytometry | IL-6, IL-10 | 7 |
| Liu et al 63 | Asian | China | HB | Multicenter, Retrospective cohort | 2044 | 61 ± 14.09 | Mild: 1087Severe: 957 | NA | CLIA | IL-6, IL-10 | 8 |
| Liu et al 64 | Asian | China | HB | Retrospective | 50 | 54 ± 20.86 | Mild: 24Severe: 26 | NA | Biochemical assay | IL-6, IL-10 | 6 |
| Liu et al 65 | Asian | China | HB | Single-center, retrospective | 51 | 43.33 ± 12.97 | Mild: 44Severe: 7 | NA | Biochemical assay | IL-6 | 6 |
| Liu et al 66 | Asian | China | HB | Retrospective cohort | 255 | 60 ± 50.7 | Mild: 214Severe: 41 | NA | Biochemical assay | IL-6, IL-10 | 7 |
| Liu et al 67 | Asian | China | HB | Retrospective cohort | 80 | 55 ± 43.3 | Mild: 11Severe: 69 | NA | ELISA | IL-6, IL-10 | 8 |
| Liu et al 68 | Asian | China | HB | Retrospective cohort | 124 | NA | Mild: 37Severe: 87 | NA | Biochemical assay | IL-6 | 7 |
| Liu et al 70 | Asian | China | HB | Retrospective cohort | 101 | 62.33 ± 17.3 | Mild: 47Severe: 54 | NA | Biochemical assay | IL-6, IL-10 | 7 |
| Liu et al 71 | Asian | China | HB | Retrospective | 76 | 47 ± 45.36 | Mild: 30Severe: 46 | NA | Biochemical assay | IL-6, IL-10 | 6 |
| Liu et al 72 | Asian | China | HB | Single-center, retrospective | 67 | Mild: 46 ± 22.79Severe: 64.77 ± 11.79Critical: 64 ± 11.21 | Mild: 10Severe: 57 | NA | Flow cytometry | IL-6, IL-10 | 6 |
| Luo et al 73 | Asian | China | HB | Multicenter, Retrospective | 1018 | 59.67 ± 14.85 | NA | Dead: 201Survivors: 817 | CLIA | IL-6, IL-10 | 9 |
| Lu et al 74 | Asian | China | HB | Single-center, retrospective | 121 | 6.25 ± 4.31 | Mild: 101Severe: 20 | NA | Flow cytometry | IL-6, IL-10 | 9 |
| Lv et al 75 | Asian | China | HB | Retrospective cohort | 354 | 58.33 ± 49.87 | Mild: 115Severe: 239 | NA | Biochemical assay | IL-6, IL-10 | 7 |
| Ma et al 76 | Asian | China | HB | Single-center, retrospective | 37 | 63.67 ± 8.48 | Mild: 17Severe: 20 | NA | Biochemical assay | IL-6 | 6 |
| Ma et al 77 | Asian | China | HB | Retrospective cohort | 84 | 50.93 ± 15.24 | Mild: 64Severe: 20 | NA | Flow cytometry | IL-6 | 7 |
| Maeda et al 78 | Caucasian | USA | HB | Single-center retrospective cohort | 224 | 63 ± 17 | Mild: 167Severe: 57 | NA | Biochemical assay | IL-6 | 8 |
| Mandel et al 79 | Caucasian | Israel | HB | Prospective non-randomized cohort | 71 | 62 ± 13.8 | NA | Dead: 12Survivors: 59 | ELISA | IL-6 | 8 |
| McElvaney et al 80 | Caucasian | Ireland | HB | Retrospective | 40 | 55.5 ± 17.7 | Mild: 20Severe: 20 | NA | ELISA | IL-6, IL-10 | 8 |
| Merza et al 81 | Caucasian | Iraq | HB | Retrospective | 56 | Mild: 35.7Severe: 51.75 | Mild: 41Severe: 15 | NA | ELISA | IL-6, IL-10 | 8 |
| Mikami et al 82 | Caucasian | USA | HB | Multicenter Retrospective cohort | 6493 | 58 ± 21.5 | Mild: 2785Severe: 3708 | Dead: 806Survivors: 2014 | Biochemical assay | IL-6 | 7 |
| Mo et al 83 | Asian | China | HB | Single-center, retrospective | 155 | 54 ± 17.96 | Mild: 70Severe: 85 | NA | Biochemical assay | IL-6 | 6 |
| Morisson et al 84 | Caucasian | USA | HB | Retrospective observational cohort | 81 | 64.33 ± 9.81 | NA | Dead: 35Survivors: 46 | Biochemical assay | IL-6 | 6 |
| Myhre et al 85 | Caucasian | Norway | HB | Prospective observational | 123 | Dead: 64.3 ± 10.7Survivors: 57.8 ± 16.3 | NA | Dead: 35Survivors: 88 | ECLIA | IL-6 | 7 |
| Nie et al 86 | Asian | China | HB | Retrospective | 97 | 43 ± 22.58 | Mild: 72Severe: 25 | NA | Biochemical assay | IL-6, IL-10 | 6 |
| Pandolfi et al 87 | Caucasian | Italy | HB | Prospective cohort | 33 | Mild: 62.67 ± 8.05Severe: 58 ± 11.33 | Mild: 5Severe: 28 | NA | ELISA | IL-6 | 8 |
| Qin et al 88 | Asian | China | HB | Single-center, retrospective | 452 | 57.33 ± 14.87 | Mild: 166Severe: 286 | NA | Flow cytometry | IL-6, IL-10 | 8 |
| Quartuccio et al 89 | Caucasian | Italy | HB | Retrospective | 24 | Dead: 68.8 ± 9.4Survivors: 65.8 ± 8.2 | NA | Dead: 6Survivors: 18 | ECLIA | IL-6 | 7 |
| Quiroga et al 90 | Caucasian | Spain | HB | Single-centered, prospective, and observational | 16 | 72 ± 15 | NA | Dead: 4Survivor s: 12 | Enzyme-immune assay | IL-6 | 7 |
| Rastrelli et al 91 | Caucasian | Italy | HB | Retrospective cohort | 31 | Mild: 61.5 ± 9.14Severe: 62.83 ± 48.15Dead: 73 ± 27.85 | Mild: 21Severe: 10 | NA | ECLIA | IL-6 | 8 |
| Ruan et al 92 | Asian | China | HB | Multicenter Retrospective cohort | 150 | Dead: 54.33 ± 49.99Survivors: 58.3 ± 27.9 | NA | Dead: 68Survivors: 82 | Biochemical assay | IL-6 | 6 |
| Sabaka et al 93 | Caucasian | Slovakia | HB | Retrospective | 45 | Mild: 80.33 ± 10.98Severe: 85.83 ± 7.61 | Mild: 26Severe: 19 | NA | ECLIA | IL-6 | 8 |
| Sarfaraz et al 94 | Asian | Pakistan | HB | Prospective cohort | 170 | Dead: 61 ± 12.57Survivors: 53 ± 13 | NA | Dead: 67Survivors: 103 | Biochemical assay | IL-6 | 6 |
| Sarhan et al 95 | African | Egypt | HB | Retrospective | 203 | 58.67 ± 23.89 | Mild: 26Severe: 19 | NA | ELISA | IL-6 | 8 |
| Shi et al 96 | Asian | China | HB | Multicenter Retrospective cohort | Zhao et al 148 | 50.58 ± 10.67 | Mild: 119Severe: 29 | NA | Biochemical assay | IL-6, IL-10 | 9 |
| Shi et al 97 | Asian | China | HB | Retrospective | 87 | 56.67 ± 49.75 | Mild: 51Severe: 36 | NA | Biochemical assay | IL-6 | 6 |
| Shi et al 98 | Asian | China | HB | Prospective observational | 45 | Mild: 40.23 ± 12.61Severe: 59.35 ± 18.07Critical: 66.9 ± 17.01 | Mild: 13Severe: 32 | NA | Biochemical assay | IL-6, IL-10 | 7 |
| Simioli et al 99 | Caucasian | Italy | HB | Single-center case-control | 29 | 64 ± 22.5 | Mild: 11Severe: 18 | NA | Biochemical assay | IL-6 | 7 |
| Song et al 100 | Asian | China | HB | Retrospective | 73 | Mild: 48 ± 17.1Severe: 55.93 ± 12.51 | Mild: 31Severe: 42 | NA | Biochemical assay | IL-6, IL-10 | 6 |
| Song et al 101 | Asian | China | HB | Single-center, retrospective cohort | 1172 | 59 ± 14.84 | Mild: 881Severe: 291 | NA | Biochemical assay | IL-6, IL-10 | 7 |
| Song et al 102 | Asian | China | HB | Cross sectional observational | 41 | 40.83 ± 12.68 | Mild: 29Severe: 12 | NA | Flow cytometry | IL-6 | 8 |
| Sun et al 103 | Asian | China | HB | Retrospective | 244 | Dead: 72 ± 9Survivors: 67.67 ± 6 | NA | Dead: 121Survivors: 123 | Biochemical assay | IL-6 | 7 |
| Sun et al 104 | Asian | China | HB | Prospective observational cohort | 99 | Mild: 52 ± 15.28Severe: 70.83 ± 14.88 | Mild: 49Severe: 50 | NA | Biochemical assay | IL-6, IL-10 | 7 |
| Sun et al 105 | Asian | China | HB | Prospective cohort | 63 | 45 ± 62.21 | Mild: 44Severe: 19 | NA | Biochemical assay | IL-6 | 6 |
| Taha et al 106 | African | Egypt | HB | Observational cohort | 85 | 54 ± 17.35 | Mild: 46Severe: 39 | Dead: 21Survivors: 64 | ELISA | IL-6 | 8 |
| Tang et al 107 | Asian | China | HB | Prospective | 120 | 58 ± 15.76 | Mild: 60Severe: 60 | NA | Flow cytometry | IL-6, IL-10 | 9 |
| Tian et al 108 | Asian | China | HB | Multicenter, retrospective, cohort | 751 | 63.33 ± 8.91 | Mild: 84Severe: 148 | NA | CLIA | IL-6, IL-10 | 9 |
| Toniati et al 109 | Caucasian | Italy | HB | Single-centered, prospective | 100 | 63.33 ± 10.53 | Mild: 77Severe: 23 | NA | Biochemical assay | IL-6 | 6 |
| Tu et al 110 | Asian | China | HB | Single-center, retrospective cohort | 174 | Dead: 71.33 ± 12.58Survivors: 50 ± 18.71 | NA | Dead: 25Survivors: 149 | Biochemical assay | IL-6 | 7 |
| Vultaggio et al 17 | Caucasian | Italy | HB | Retrospective observational cohort | 208 | 65.7 ± 15 | Mild: 145Severe: 63 | NA | ELISA | IL-6 | 8 |
| Wan et al 111 | Asian | China | HB | Prospective | 66 | Mild: 43.05 ± 13.12Severe: 61.29 ± 15.55 | Mild: 45Severe: 21 | NA | Flow cytometry | IL-6, IL-10 | 8 |
| Wang et al 112 | Asian | China | HB | Retrospective | 28 | 68.6 ± 9 | Mild: 14Severe: 14 | NA | Biochemical assay | IL-6, IL-10 | 6 |
| Wang et al 113 | Asian | China | HB | Multicenter, retrospective | 165 | 45.67 ± 11.97 | Mild: 115Severe: 50 | NA | Biochemical assay | IL-6 | 7 |
| Wang et al 114 | Asian | China | HB | Retrospective | 339 | 70 ± 8.19 | NA | Dead: 65Survivors: 274 | Biochemical assay | IL-6 | 6 |
| Wang et al 115 | Asian | China | HB | Single-center, retrospective, descriptive | 125 | 38.76 ± 13.799 | Mild: 100Severe: 25 | NA | Biochemical assay | IL-6 | 6 |
| Wang et al 116 | Asian | China | HB | Retrospective case-control | 43 | Mild: 43.05 ± 13.12Severe: 61.29 ± 15.55 | Mild: 35Severe: 8 | NA | Flow cytometry | IL-6. IL-10 | 8 |
| Wang et al 117 | Asian | China | HB | Retrospective cohort | 43 | 46.33 ± 20.44 | Mild: 36Severe: 7 | NA | Biochemical assay | IL-6, IL-10 | 7 |
| Wang et al 118 | Asian | China | HB | Retrospective | 59 | 67.4 ± 11.3 | NA | Dead: 41Survivors: 18 | CLIA | IL-6, IL-10 | 6 |
| Webb et al 119 | Caucasian | USA | HB | Prospective observational cohort | 72 | 55.67 ± 18.62 | Mild: 5Severe: 67 | NA | Biochemical assay | IL-6 | 6 |
| Wei et al 120 | Asian | China | HB | Retrospective | 252 | 64.8 ± 13.3 | Mild: 131Severe: 98 | NA | CLIA | IL-6, IL-10 | 9 |
| Wu et al 121 | Asian | China | HB | Retrospective cohort | 201 | 51.33 ± 12.69 | Mild: 117Severe: 84 | Dead: 44Survivor s: 40 | Biochemical assay | IL-6 | 6 |
| Wu et al 122 | Asian | China | HB | Single-center, retrospective cohort | Zhao et al 148 | 75 ± 78.61 | Mild: 60Severe: 88 | NA | Biochemical assay | IL-6, IL-10 | 6 |
| Wu et al 123 | Asian | China | HB | Retrospective | 71 | 57 ± 21.19 | Mild: 32Severe: 39 | NA | Flow cytometry | IL-6, IL-10 | 8 |
| Xiao et al 124 | Asian | China | HB | Retrospective | 143 | NA | Mild: 107Severe: 36 | NA | Biochemical assay | IL-6 | 6 |
| Xie et al 125 | Asian | China | HB | Retrospective | 29 | 64.1 ± 14.95 | Mild: 22Severe: 7 | NA | Biochemical assay | IL-6 | 7 |
| Xu et al 126 | Asian | China | HB | Single-centered, retrospective observational | 187 | 60.5 ± 16.81 | Mild: 80Severe: 107 | Dead: 28Survivors: 117 | Biochemical assay | IL-6, IL-10 | 7 |
| Xu et al 127 | Asian | China | HB | Multicenter Retrospective observational | 324 | 63.2 ± 14.5 | Mild: 177Severe: 147 | NA | Biochemical assay | IL-6 | 8 |
| Xu et al 128 | Asian | China | HB | Retrospective | 155 | Mild: 39.84 ± 15.09Severe: 50.97 ± 13.55 | Mild: 125Severe: 30 | NA | Biochemical assay | IL-6 | 6 |
| Xu et al 69 | Asian | China | HB | Single-center, retrospective cohort | 88 | 57.11 ± 15.39 | Mild: 47Severe: 41 | NA | Biochemical assay | IL-6 | 6 |
| Xu et al 129 | Asian | China | HB | Multicenter Retrospective | 69 | 56.33 ± 19.69 | Mild: 44Severe: 25 | NA | Flow cytometry | IL-6 | 9 |
| Yan et al 130 | Asian | China | HB | Single-centered, retrospective observational | 48 | 69.4 ± 9.9 | NA | Dead: 39Survivors: 9 | Biochemical assay | IL-6 | 6 |
| Yang et al 131 | Asian | China | HB | Single-center, retrospective | 93 | 46.4 ± 17.6 | Mild: 69Severe: 24 | NA | Flow cytometry | IL-6, IL-10 | 8 |
| Yang et al 132 | Asian | China | HB | Retrospective | 76 | NA | Mild: 42Severe: 34 | NA | Biochemical assay | IL-6, IL-10 | 6 |
| Yang et al 133 | Asian | China | HB | Retrospective observational | 55 | 44 ± 15.23 | Mild: 21Severe: 34 | NA | Biochemical assay | IL-6 | 6 |
| Yang et al 134 | Asian | China | HB | Retrospective case-control | 45 | 32 ± 29.87 | Mild: 23Severe: 22 | NA | Flow cytometry | IL-6 | 8 |
| Yuan et al 135 | Asian | China | HB | Retrospective | 189 | 60.33 ± 14.94 | Mild: 102Severe: 87 | NA | Biochemical assay | IL-6 | 6 |
| Yuan et al 136 | Asian | China | HB | Retrospective | 117 | 64.67 ± 10.51 | Mild: 53Severe: 54 | NA | Biochemical assay | IL-6, IL-10 | 6 |
| Zeng et al 137 | Asian | China | HB | Retrospective | 49 | Mild: 46 ± 19Severe: 60 ± 16Critical: 68 ± 20 | Mild: 28Severe: 21 | NA | Biochemical assay | IL-6, IL-10 | 6 |
| Zeng et al 138 | Asian | China | HB | Retrospective | 317 | 61 ± 14.15 | Mild: 93Severe: 224 | NA | CLIA | IL-6, IL-10 | 8 |
| Zhang et al 139 | Asian | China | HB | Retrospective | 222 | 61 ± 12.69 | Mild: 81Severe: 67 | NA | Automated immunoassay multiplex array system | IL-6, IL-10 | 8 |
| Zhang et al 140 | Asian | China | HB | Retrospective | 82 | 72.5 ± 11.32 | NA | Dead: 82Survivors: 0 | Automated immunoassay multiplex array system | IL-6 | 8 |
| Zhang et al 141 | Asian | China | HB | Retrospective case-series | 98 | 63.9 ± 1.4 | NA | Dead: 36Survivors: 62 | Biochemical assay | IL-6 | 7 |
| Zhang et al 142 | Asian | China | HB | Retrospective | 43 | Mild: 44.4 ± 15.9Severe: 61.9 ± 9.4 | Mild: 29Severe: 14 | NA | ELISA | IL-6, IL-10 | 8 |
| Zhang et al 143 | Asian | China | HB | Single-center, retrospective | 111 | 42.33 ± 18.78 | Mild: 93Severe: 18 | Dead: 18Survivors: 93 | Biochemical assay | IL-6, IL-10 | 7 |
| Zhang et al 144 | Asian | China | HB | Retrospective | 134 | 60.78 ± 12.98 | Mild: 33Severe: 101 | Dead: 101Survivors: 33 | Biochemical assay | IL-6 | 6 |
| Zhang et al 145 | Asian | China | HB | Single-center retrospective observational | 74 | 63.33 ± 12.10 | Mild: 47Severe: 27 | NA | Biochemical assay | IL-6 | 7 |
| Zhang et al 146 | Asian | China | HB | Retrospective | 38 | Dead: 37.7 ± 8.2Survivors: 35.8 ± 4.1 | NA | Dead: 18Survivors: 20 | Biochemical assay | IL-6 | 6 |
| Zhang et al 147 | Asian | China | HB | Retrospective | 326 | 51.33 ± 54.36 | Mild: 28Severe: 293 | NA | Flow cytometry | IL-6 | 8 |
| Zhao et al 149 | Asian | China | HB | Single-center, retrospective | 172 | 64.33 ± 10.47 | Mild: 112Severe: 60 | NA | Biochemical assay | IL-6, IL-10 | 7 |
| Zhao et al 150 | Asian | China | HB | Prospective | 71 | 49.33 ± 19.67 | Mild: 53Severe: 18 | NA | Bio plex multiplex immunoassay | IL-6, IL-10 | 8 |
| Zheng et al 150 | Asian | China | HB | Single-center, Retrospective cohort | 96 | 54.7 ± 15.43 | Mild: 22Severe: 74 | NA | Biochemical assay | IL-6, IL-10 | 7 |
| Zheng et al 151 | Asian | China | HB | Retrospective | 34 | 66.67 ± 13.93 | Mild: 19Severe: 15 | NA | ELISA | IL-6, IL-10 | 8 |
| Zhou et al 41 | Asian | China | HB | Multicenter, retrospective, cohort | 191 | 56.33 ± 15.69 | NA | Dead: 54Survivors: 137 | Biochemical assay | IL-6 | 7 |
| Zhou et al 152 | Asian | China | HB | Single-center, retrospective | 21 | 66.10 ± 13.94 | Mild: 8Severe: 13 | NA | Automatic biochemical analyzer | IL-6 | 9 |
| Zhu et al 153 | Asian | China | HB | Retrospective | 127 | 50.90 ± 15.26 | Mild: 111Severe: 16 | NA | Flow cytometry | IL-6, IL-10 | 8 |
| Zou et al 154 | Asian | China | HB | Retrospective | 121 | 63.83 ± 12.38 | Mild: 69Severe: 52 | Dead: 14Survivors: 107 | Biochemical assay | IL-6, IL-10 | 7 |
Abbreviations: CLIA, chemiluminescent immunoassay; ECLIA, electro-chemiluminescent immunoassay; ELISA, enzyme-linked immunosorbent assay; HB, hospital based; NA, not available; NOS, Newcastle Ottawa Scale; OLHDF, online hemodiafiltration.