PATIENTS only learned by phone that they had tested positive for a potentially fatal heart condition.
The manner in which patients were told emerged as a hospital began a major probe into a delay issuing results.
Support group Heart Children Ireland warned it was "very concerned" to learn of the blunder at the National Centre for Medical Genetics located in Our Lady's Hospital for Sick Children in Crumlin.
The hospital confirmed all 69 patients who recorded "abnormal" results have now been contacted. "There has been no indication that any patient has suffered any adverse effects as a result of the delayed notification of test results," a spokesman stated.
The patients had all been referred by specialist inherited heart disease clinics. Margaret Rogers, CEO of Heart Children Ireland, which supports 1,000 families of children born with congenital heart defects, called on the hospital to ensure proper protocols were in place to deliver results promptly.
"We are extremely concerned that something that could have such serious outcomes as this could happen in the hospital," said Ms Rogers.
Dr Angie Brown, Irish Heart Foundation medical director and consultant cardiologist, said concerns over sudden cardiac death were the main reasons people seek genetic screening tests.
"The families going may have a history of sudden cardiac death, or someone collapses, or they record an abnormal ECG," the consultant explained.
The tests, carried out free of charge, involve a blood test and a DNA analysis which is processed at the centre before being sent abroad for testing.
Dr Brown was informed by the centre that those contacted so far with abnormal results had not suffered any cardiac events as they awaited the delayed test results.
Dr Deirdre Ward, director of the Centre for Cardiovascular Risk in Younger Persons, which offers heart screening services for families affected by sudden cardiac death, said it kept a full record of all patients referred to the centre for genetic testing and kept in contact with the Crumlin centre on the results.
One concerned parent of a child with suspected heart problems told the Irish Independent that her child had been "in and out of Crumlin" and had undergone genetics tests to determine the cause.
She said that they were waiting months for test results to come back, and it seemed that a number of results had been "left sitting".
She added that she was in the process of contacting her solicitor for advice about the apparent blunder.
The centre confirmed it had identified the cause of the delay in communicating the results and a member of staff had been suspended from duty pending a full investigation.
The hospital only became aware there was an issue last week after it received phonecalls from patients expressing concerns. Now all 506 tests – 428 adults and 78 children – for inherited cardiac disease carried out between February 2011 and November 2013 are being reviewed.
The 69 children and adults whose results were abnormal, but were not informed promptly, will now be offered an appointment with a genetic consultant within one week.
The hospital stated it "apologises" for distress caused.
Genetically inherited diseases – such as Long QT Syndrome – cause a defect in the heart rhythm that can lead to fainting spells and, in the worst cases, sudden death.
Dr Brown pointed out heart arrhythmias such as these can be managed and treated if diagnosed correctly. But the consultant stressed it would be hard to assess the level of risks caused by the delays as the circumstances of each case differ.