A hospital trust is contacting thousands of patients who may have been given the wrong blood test results.
As many as 11,000 people could be affected – with some potentially misdiagnosed as diabetic.
Bedfordshire Hospitals NHS Foundation Trust said it experienced an “intermittent issue” with the machines that analyse HbA1c blood tests on certain dates in April and July.
An HbA1c blood test measures a person’s average blood sugar levels and is used to diagnose and monitor diabetes.
Those with the condition tend to have higher HbA1c levels than non-diabetics.
The trust warned in a statement on its website the issue with its machine “may have resulted in some patients receiving HbA1c results that were potentially higher than actual”.
The issue is only related to tests analysed on machines at the laboratory in Luton and Dunstable University Hospital.
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The trust said patients across Luton, south Bedfordshire and Hertfordshire who had received “incorrect” test results were being invited for retests as a precaution.
It apologised for any “emotional distress and inconvenience” caused and said a “detailed review to find out what went wrong” was being carried out.
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The trust urged patients not to turn up for a repeat test unless they had been contacted by the hospital by phone or letter.
The statement said: “Although we understand any patient will be concerned to learn their blood test might have been wrong, it is important not to worry.”
It added: “As a precautionary measure we are no longer analysing these results at our Luton lab.
“The repeat blood sample is going to be sent to another hospital laboratory to be analysed, until we are sure the Luton hospital analysers are performing accurately again.”