When Ita and Robert Booth's beautiful teenage daughter Sarah waved goodbye to her parents on a sunny Saturday afternoon last June, the couple had no idea that less than 24 hours later, and without any warning, their youngest child would be dead - a victim of Sudden Adult Death Syndrome (SAS), a condition that claims the lives of at least 12 apparently fit and healthy young people every week in the UK.

The academically talented Wellington College pupil, who had ambitions to be a journalist, was just 15-years-old when she died on June 20 2010.  The shocking loss has left Robert, Ita, Sarah's older sister Claire (20) and brother Owen (17) devastated, yet determined to raise awareness of an increasingly frequent syndrome that snatches away the lives of young people in their prime. 

"Sarah was just wonderful," says Ita. 

"She was like a breath of fresh air.  When she walked into the room, everybody noticed her.  She was just a fabulous girl. 

"She was very academic and also sporty.  She loved netball and had achieved grade five at ballet. 

"The weekend before her death, Robert and I had gone to Rome for our 25th wedding anniversary and I remember us saying how sweet life was.  Little did we realise that seven days later our family would be torn apart." 

The events of that terrible night are still painfully clear for the south Belfast family. 

Recalls Ita:  "On Saturday June 19 , Sarah had headed off into town in the afternoon before going on to a sleepover at a friend's house.  She texted me in the early evening to say that she had bought some new clothes. 

"Robert and I went to bed around midnight as normal.  We didn't know that Sarah  had texted her sister, Claire saying that she had a pain in her back. Claire texted back and told her to lie down.  

"At about 4am, the doorbell went.  I knew our son had been out and I hadn't heard him return, so I thought something had happened to him. 

"Robert went downstairs and the policewoman told him that Sarah was on her way to the Ulster Hospital with a very faint pulse and no respiratory signs. 

"They took us to the hospital and, after a short while, the dreaded three or four doctors came and told us that they had tried their best but were unable to save Sarah and that she was dead, 

"It wasn't until the next morning that Claire saw a text that arrived at 2am from Sarah, saying that she had vomited. 

"A few days later, the police told us they had interviewed everyone who was at the house and that there had been nothing untoward happening.  It had been a completely innocent teenage party.  The staff at the coroner's office knew how concerned and upset we were and were able to tell us within a few weeks that the toxicology report showed no sign of drugs or alcohol and that Sarah's heart tissue had been sent to London for further analysis." 

It may be almost a year since the tragedy, but for Ita, a staff officer with the Department for Environment , the pain of losing Sarah has become worse, not better. 

She says: "The suddenness of what happened left us all in total shock for six months.  I felt completely numb and it's actually worse now that the reality that Sarah is really gone has sunk in.  I haven't been able to go back to work and I don't know if I will ever be able to.  Robert, a business advisor for Invest NI, found it very difficult to go back. 

"After Sarah died, her classmates called quite a lot and at the beginning I was OK with that because I was numb with shock.  Now I find it really hard and feel almost jealous of them. 

"Christmas was so bad that we took ourselves away to a remote cottage and the four of us tried to get through the days in front of a wood-burning stove.  Robert and I went out an wrote Sarah's name in the sand and tried to cope as best we could. 

The final coroner's report that Robert and Ita received a few months after Sarah's death confirmed that she had suffered Sudden Adult Death syndrome.  But there was further distress to come. 

Even though there was no history of heart disease in the family, the results from the heart tissue analysis in London came back with a recommendation that all members of Sarah's immediate family be screened for heart abnormalities as they suspected her heart may have had an electrical imbalance and had gone into a dangerous type of arrhythmia (heart rhythm). 

"Everyone was normal apart from Claire, whose heart showed an abnormality - long QT syndrome (an abnormality of the heart's electrical syndrome) - where the time between heartbeats is irregular and sometimes too long.  Sarah may have suffered from it as well but we don't know as it can only be spotted when a heart is actually beating," says Ita. 

"The condition can be treated with beta-blockers but it's made Claire and the whole family very, very scared. 

"They also did blood tests and there was an increased level of an enzyme in Claire's blood and she was immediately hospitalised on New Year's Day and was monitored for six days. 

"An MRI scan also showed an inflammation of the heart and she was put on an ace-inhibitor and beta-blockers straight away.  She had another EGG recently, which was still abnormal and she has to go for another MRI scan in a few days to see in the inflammation has gone down. 

"As well as her grief for her sister, Claire now feels that there is a big black could hanging over her head. 

"Strangely, when she was younger, Sarah had said to me a few times that she thought there was something wrong with her heart.  I took her to the doctor and she was given an EGG which turned out normal and she didn't complain any more after that." 

As a tribute to Sarah, her former schoolmates at Wellington College are running a number of relay teams in the Belfast Marathon to raise money for the charity CRY (Cardiac Risk in the Young).  And although it will be painful for Ita and the family to see, each runner will be wearing a T-shirt with Sarah's face printed on the front. 

Ita says: "I don't know if we'll be able to bear it but knowing the sort of girl Sarah was - she would have loved to have her face on a T-shirt - and we are hoping we will be strong enough to go along and watch. 

"I would love to be able to say that I feel a part of her is still with me but at the moment I don't, and that makes me feel so heartbroken.  I hope at some time I will be able to feel that, but now, it's like a part of me died with Sarah and I'd give anything just to feel her around me." 

It was through the bereavement charity Cruse that Ita first heard about CRY which she says has provided invaluable support for the whole family. 

"My Cruse counsellor told me about the charity and we contacted them for an information pack. 

"They got back to me by email and were fantastic.  Chief executive Alison Cox telephoned me herself. 

"We then went to a bereavement day and were able to talk to other parents who had lost children in a similar way and who really understood what we were going through. 

"There was a husband and wife who were there with their daughter, Heather.  Their other daughter, Carol had died suddenly while she was sleeping in her bed. 

"Claire and Heather arranged to meet and support each other and they got on really well. 

"I'll never be able to come to terms with Sarah's death and I don't think I'll ever be alright but I hope someday that I'll be able to learn to cope with the pain. 

"I don't like the words 'moving on', but learning to cope is what I would like to able to do - eventually." 

HOW CHARITY WORKS TO IDENTIFY THOSE YOUNG PEOPLE AT RISK

Founded in 1995, CRY aims to raise awareness of the risk of undetected cardiac abnormalities in young people and reduce the frequency of young, sudden cardiac death by working with heart specialists and with family doctors to establish screening facilities to promote and protect the cardiac health of our young people. 

As well as working with the Department for Health and others to develop  high quality cardiac services, CRY provides funding to the NHS to help fast-track the complex range of services need (following a sudden cardiac death, to determine the risk to other family members. 

The charity also runs a regional  bereavement support network and counselling services for families affected.

To contact CRY telephone 01737 363 222 or email them at cry@c-r-y.org.uk. 

Further information about the charity can be found on their website at: www.c-r-y.org.uk

To contact Cruse Bereavement Care, call: 0844 477 9400 or email: helpline@cruse.org.uk