On 4 March, South West London Pathology (SWLP) identified an issue with Faecal Immunochemical Test (FIT) test results from between 27 December 2025 to 4 March 2026. During this period, some results were issued that were falsely high (positive).
All results that went out from 5 March onwards are correct.
The FIT test looks for tiny amounts of blood in poo. A GP might give this test as part of the investigation into symptoms which could be caused by bowel cancer. Traces of blood in poo can be caused by other medical conditions, and a high level of blood does not necessarily mean cancer.
Once the mistake was identified, all results were corrected and resent to affected patients’ GPs and clinical teams.
Patients do not need to have the test done again as their GPs and clinical teams now have the updated correct result.
No cancers have been missed because of this error. However, some patients may have been referred urgently for further tests such as a colonoscopy or CT colonoscopy that they did not need.
The hospitals that undertook the colonoscopies or CT colonoscopies are reviewing all the cases. Any patients who may have had an unnecessary investigation will be contacted.
Some questions and answers are available which give more information about this issue, including what caused the error and what the laboratory is doing as a result.
Faecal Immunochemical Test (FIT) results error – frequently asked questions
If you want further information, you can email SWLPComms@stgeorges.nhs.uk.