Around a fifth of former patients of Belfast-based neurologist Dr Michael Watt received an "insecure diagnosis," according to a new report.
An ongoing public inquiry is examining the work of the now retired neurologist.
Around 2,500 patients were initially recalled by the Belfast Trust following a probe into the work of Dr Watt.
Speaking in the Stormont Assembly, Health Minister Robin Swann said of the second cohort of Dr Watt's patients to be reviewed, which involved 927 patients, almost 20% had "not secure" diagnosis.
Mr Swann said it is important to note that a diagnosis which is considered to be not secure "does not automatically equate to a misdiagnosis".
"Other factors need to be considered. The patients involved have been advised of the outcome of their individual cases," he said.
Mr Swann also said around three quarters of patients in the second cohort were considered to have a 'secure' diagnosis.
Meanwhile, for just under 5% of patients, there was uncertainty in respect of whether the previous diagnosis was secure.
Mr Swann said that while a higher proportion of the second cohort of patients to be reviewed were assessed as having a secure diagnosis than for cohort one - almost 76% from 68% - there remained approximately one fifth of patients with an insecure diagnosis.
In another development, the Belfast Health Trust has recalled a further 209 neurology patients in connection with the work of Dr Watt.
They are former patients of Dr Watt who were seen and discharged between 1996 and 2012, and who are taking certain prescribed medications for specific neurological conditions.
Those affected will receive a letter asking them to contact the Trust to set up a telephone review with a consultant neurologist.
These should be completed within 4 weeks.
Speaking about the latest recall, the Chief Executive of the Belfast Trust, Dr Cathy Jack Trust Chief Executive, Dr Cathy Jack said:
"I am truly sorry that we have had to recall a further 209 people. I absolutely understand that this will cause worry and anxiety to a number of people and their families and I am deeply sorry for that.
"I also accept this next stage may be very difficult for those patients who have already been reviewed and whose diagnoses may have been changed as a result of our two previous recalls.
"It is absolutely imperative that we put right any past wrongs and while this is painful, it is vital we assure ourselves that former patients, now discharged and who are taking very specific medication, are taking it for the correct reasons.’
Video report by Deborah McAleese: