It has been revealed almost 100 smear tests have been lost as they were en route to a laboratory.
The University College London Hospitals NHS Trust confirmed that 90 samples from GP surgeries never arrived at its laboratory.
The women affected have been told to have a repeat test and that their results will be "fast-tracked".
A statement said: "The trust very much regrets that a number of cervical smear test samples have been lost in transit between some GP practices and the hospital.
"Although there is every indication that the samples were sent by the practices, we have no evidence that they were received by the laboratory."
Local GP practices are being told to check that no other tests have gone missing.
The trust has apologised for the "distress" caused to its patients and said an investigation is under way to establish what happened and ensure there is no reoccurrence.
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University College London Hospitals NHS Trust