Tests on the bone growth of certain asylum-seekers to determine their real age have shown that nine out of 10 who claimed to be minors were adults.
The tests were introduced recently after concerns that adults could be placed in accommodation for asylum-seekers alongside vulnerable children who are separated from their parents.
Out of some 40 asylum-seekers for whom test results have been returned to the authorities, four have been shown to be minors (under 18) while the rest are adults, according to officials.
Age testing of asylum-seekers through bone age determination is used in several other EU countries, although there have been widespread concerns about the accuracy of such procedures. The tests involve the assessment of bone growth by X-rays of applicants' left wrists.
The Office of the Refugee Applications Commissioner, which assesses asylum claims, says where tests have shown applicants to be in the age range of 17 to 19, they "err on the side of caution" and recognise them as minors.
This has been welcomed by refugee lobby groups, who also say applicants should be tested only in extreme cases and that the bone assessment should be accompanied by a psychological test.
Unaccompanied minors seeking refugee status in the Republic are entitled to more generous social welfare benefits than adults. They are exempted from the system of "direct provision" where full board accommodation is provided and weekly social welfare payments are reduced to €19 per adult. Minors receive normal social welfare payments and are placed in hostels, B&Bs or residential or foster care in Dublin under the care of the East Coast Area Health Board.
TCD's professor of anatomy, Dr Moira O'Brien, said there is "quite a margin of error" in bone tests. While malnutrition or infection can impede the bone maturation process, injuries can accelerate it. The results can also vary between males and females, as the process can be accelerated by the early onset of menstruation which is common among girls from the Tropics, she added. Last year, 603 asylum applications were taken from unaccompanied minors from more than 50 countries, with the majority coming from Nigeria. This is double the figure for the previous year.
Until last October, most unaccompanied minors seeking refugee status were not able to have their cases fully processed, due to the lack of expertise among government officials who have subsequently undergone UNHCR training. The UNHCR's Irish representative, Ms Pia Prutz Phiri, said age testing was acceptable "in extreme cases where there are very serious reasons for believing that someone claiming to be a separated child is not a child."
Mr Dug Cubie, of the Irish Refugee Council, said he had concerns about the use of such tests on teenagers from African states whose bone development may be different from the European norm.