Jonathon had attended Altnagelvin Hospital with a heart condition and as he wasn't happy with his diagnosis he requested his medical records.
He told the Shaun Doherty Show today of his shock that his file contained 70 pages of another person's medical records:
Responding the Western Health Trust said it is investigating the matter which it is taking very seriously.
In a statement it said that there are many thousands of medical records used everyday and the Trust experiences very small numbers of data breaches annually.
The trust says it is working to address the error with those involved and the service area concerned.