Table 1. Baseline characteristics of eligible studies for this meta-analysis.
| Study | Year | Patients, n | Country | Tumor type | Period | Age (years) Median/mean (range) | Ethnicity | Specimen | Detection method | Treatment | Cut-off value | Endpoint | NOS score |
| Tamai | 2014 | 91 | Japan | eCCA | 2000-2008 | NA | Asian | Tissue | IHC | Surgical resection | Moderate or intense staining | OS | 6 |
| Gani | 2016 | 54 | USA | iCCA | 1991-2011 | Mean: 64 | Caucasian | Tissue | IHC | Surgical resection | >5% tumor cells | OS | 8 |
| Ma | 2017 | 70 | China | eCCA | 2009-2013 | Mean: 62.5 Range: 33-83 |
Asian | Tissue | IHC | Surgical resection | >50% tumor cells | OS | 8 |
| Sangkhamanon | 2017 | 46 | Thailand | iCCA, eCCA | NA | Median: 57.5 Range: 45-76 |
Asian | Tissue | IHC | Surgical resection | >1% tumor cells | OS | 6 |
| Walter | 2017 | 69 | Germany | eCCA | 2007-2015 | NA | Caucasian | Tissue | IHC | Surgical resection | Score 3 | OS | 6 |
| Kim | 2018 | 34 | USA | eCCA | 1990-2015 | Median: 67 Range: 42-86 |
Caucasian | Tissue | IHC | Surgical resection | >1% tumor cells | OS, DFS | 8 |
| Lin | 2018 | 66 | China | GBC | 2009-2014 | Median: 65 Range: 29-81 |
Asian | Tissue | IHC | Surgical resection | >5% tumor cells | OS, DFS | 8 |
| Ueno | 2018 | 117 | Japan | eCCA | 1995-2006 | Median: 71 Range: 44-87 |
Asian | Tissue | IHC | Surgical resection | Score 2 | OS | 8 |
| Zhu | 2018 | 192 | China | iCCA | NA | NA | Asian | Tissue | IHC | Surgical resection | >5% tumor cells | OS, DFS | 7 |
| Ahn | 2019 | 183 | Korea | eCCA | 2003-2013 | Median: 68 Range: 41-83 |
Asian | Tissue | IHC | Surgical resection | >1% tumor cells | OS, DFS | 8 |
| Dong | 2019 | 125 | China | iCCA | 2012-2013 | Mean: 49 Range: 29-65 |
Asian | Tissue | IHC | Surgical resection | >5% tumor cells | OS, DFS | 7 |
| Kitano | 2019 | 177 | Japan | iCCA, eCCA | 2005-2014 | NA | Asian | Tissue | IHC | Surgical resection | >25% tumor cells | OS | 7 |
| Kriegsmann | 2019 | 170 | Germany | iCCA, eCCA | 1995-2010 | Median: 63 Range: 31-91 |
Caucasian | Tissue | IHC | Surgical resection | >1% tumor cells | OS | 8 |
| Lu | 2019 | 320 | China | iCCA | 2005-2011 | Median: 58 | Asian | Tissue | IHC | Surgical resection | >5% tumor cells | OS | 8 |
| Yu | 2019 | 62 | China | eCCA | 2015-2017 | Mean: 60.8 Range: 22-81 |
Asian | Tissue | IHC | Surgical resection | Score 3 | OS, DFS | 8 |
NA, not available; iCCA, intrahepatic cholangiocarcinoma; eCCA, extrahepatic cholangiocarcinoma; GBC, gallbladder cancer; IHC, immunohistochemistry; OS, overall survival; DFS, disease-free survival; NOS, Newcastle-Ottawa scale.