NZ takes lead in blood clot study

By MONIQUE DEVEREUX health reporter

One of the world's most comprehensive studies into the link between air travel and potentially fatal blood clots is likely to start in New Zealand this month.

Up to 1000 volunteers will take part, using for the first time a special blood test.

Doctors from Green Lane Hospital and Wellington Hospital, who have worked on the project for six months, hope to get approval from the Health Ministry's Auckland Ethics Committee this week.

The project aims to find exactly who is in danger of developing economy class syndrome - when blood clots form in the veins and travel to the heart or lungs - and why.

A British study already completed and an Australian one due to start have not targeted as many people, and are looking at travellers - usually with a scan of the lungs - only after their long-haul flights.

The New Zealand project, costing up to $250,000, is being headed by Dr Rodney Hughes, a senior respiratory registrar at Green Lane.

He said volunteers would have blood tests before and after their flights. The highly sensitive test identifies blood clots.

If a patient initially tested negative for clots but gave a positive blood test on return from overseas, more tests, including lower limb and chest scans, would be done.

Volunteers also have to fill out questionnaires about their behaviour on the flight - whether they slept the entire way, if they exercised or if they took any preventive medication such as aspirin.

The blood test central to the study - called a D-dimer test - is available in New Zealand only at North Shore Hospital, although it is used in other countries. It was developed in Geneva to diagnose blood clots.

Dr Hughes said the research project "could well offer the travelling public some very worthwhile results," because of the large number of people to be surveyed and because of the accuracy of the blood test.

With Ethics Committee approval, the study could start "almost immediately, funding permitting."

It would take six months, and volunteers would be sought from Auckland and Wellington.

They would be assessed at either Green Lane or Wellington Hospital, although their blood samples would be checked at North Shore Hospital.

Air travellers believed to be most in danger of developing economy class syndrome are those who have a family history of blood clots or circulation problems, people who are obese or pregnant women.

But in the proposal to the Ethics Committee, Dr Hughes says some people treated for economy class syndrome "do not fit the typical risk pattern associated with this disease."

One top athlete suspected of being affected by the syndrome is Scottish squash champion Pamela Nimmo, who was recovering in Edinburgh Royal Infirmary over the weekend after suffering blood clots.

Nimmo had suffered breathing difficulties and lung pain over the past month.

Last month, she twice made transatlantic trips to play tournaments and exhibition matches.

In New Zealand, 55-year-old Christchurch builder Harry Cerecke is still feeling the effects of a clot diagnosed after he flew economy class to Frankfurt last October.

Doctors in Germany said he was "an inch away from death" after the clot moved from his leg to his lungs.

The Geneva-based International Air Transport Association has told airlines they should warn travellers of the risk of developing blood clots on long-haul flights.

Air New Zealand already stamps tickets, timetables and itineraries with a notice advising passengers what they can do to reduce the risk of economy class syndrome, and has included new advice about blood clots in its in-flight video.

But some doctors do not believe in economy class syndrome.

At a conference in Sydney last Friday, attended by Australian and New Zealand airline officials, unions and medical specialists, the Australasian Society of Thrombosis and Haemostasis said the risk had been vastly overstated.

Society president Dr Ross Baker said blood clots could just as easily occur on long bus trips or drives.

Scientists from Griffith University's aviation medicine centre went further. "Economy class syndrome does not exist," said the centre's Paul Bates.

Herald Online feature: Economy class syndrome