Infrared temperature screening devices at border crossings should be replaced with other more effective methods, researchers have suggested.
A University of Hong Kong study recently found that the current screening method missed 13 per cent of those who had fever, as the devices in use were not sensitive enough. "[Infrared thermography is] unsuitable as a routine screening tool for febrile conditions, especially at border crossings with huge numbers of passengers," researchers from the university's earth sciences department wrote in their report, which was published in the Hong Kong Medical Journal yesterday.
They suggested that the method be replaced with one of greater sensitivity and specificity instead, as infrared thermographic temperatures had only a moderate correlation with core temperatures.
The researchers studied 1,517 patients at the Queen Mary Hospital's accident and emergency department in 2005 and 2006.
The patients' frontal, forehead and lateral temperatures were detected with a US-made infrared camera, and then compared with their core temperatures taken by oral or aural measurements.
Forehead temperature measurement was found to be the least sensitive among the three.
Those who did not have a fever had forehead temperatures that were on average lower than their core temperatures by three degrees Celsius. The difference is 3.9 degrees among those with fever - meaning a core temperature of more than 38 degrees.
Even with frontal and lateral measurements taken alongside the forehead temperatures, 13 per cent of the people with fever were missed.
Dr Leung Ting-hung, controller of the Centre for Health Protection, said the infrared cameras at Hong Kong's border crossings had been tested before they were put into use.
He agreed that there was a difference between skin and core temperatures, but said the infrared measurements were better than having none at all, and that the method would not hold up people at the crossings.