Summary of findings 1. Summary of results table: different cut‐offs.
| Review question: What is the accuracy of single‐measurement blood CEA as a triage test to prompt further investigation for colorectal cancer recurrence after curative resection? | ||||
| Population: adults with no detectable residual disease after curative surgery (with or without adjuvant therapy) | ||||
| Studies: cross‐sectional diagnostic test accuracy studies, cohort studies, and RCTs, reporting 2 x 2 data | ||||
| Index test: Blood carcino‐embryonic antigen (CEA) | ||||
| Reference standard: appropriate¹ imaging, histology, or routine clinical follow‐up | ||||
| Setting: primary or hospital care. | ||||
| Subgroup | Number (Studies) | Sensitivity (95% CI) | Specificity (95% CI) |
Interpretation Assuming a constant incidence of 2%² recurrence at each measurement point, testing 1000 people will have the following outcome depending on the CEA threshold applied |
| 2.5 µg/L | 1515 (7) | 82% (78 to 86) | 80% (59 to 92) | 16 cases of recurrence will be detected and 4 cases will be missed. 196 people will be referred unnecessarily for further testing |
| 5 µg/L | 4585 (23) | 71% (64 to 76) | 88% (84 to 92) | 14 cases of recurrence will be detected and 6 cases will be missed. 118 people will be referred unnecessarily for further testing |
| 10 µg/L | 2341 (7) | 68% (53 to 79) | 97% (90 to 99) | 14 cases of recurrence will be detected and 6 cases will be missed. 29 people will be referred unnecessarily for further testing |
1as defined in the Reference standards section of the Methods. 2three‐monthly prevalence is estimated as 2%, as the median prevalence amongst the included studies was 30% and a standard follow‐up schedule will include 14 to 15 CEA tests over five years.