Tape measures allow researchers to measure limb circumference near the knees, feet and ankles. However, Budge said, the method can be difficult to standardize and unreliable in assessing leg volume because of bumpy, uneven skin surfaces caused by the swelling.
The water displacement procedure entails patients submerging a leg in a water tank and then measuring how much water is displaced. Each leg is done separately. "This is the gold standard for measuring limb volume, but it is cumbersome and impractical to use in field studies," Budge said. "Some patients have lymphedema so severe, they have difficulty getting a leg into the water tank or standing still long enough for all the water to drain out. Or they may have open wounds that complicate the process."
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The study showed that the infrared scanner provided measurements of leg volume and of limb circumference at multiple points that were just as accurate and precise as those obtained by tape measure and water displacement.
"But the most encouraging news is that the scanner produced highly accurate results in only a fraction of the time of the other tests," Budge said.
Researchers found that the average time required for scanner measurements of both legs was 2.2 minutes. In comparison, the tape measure and water displacement methods took an average of 7.5 minutes and 17.4 minutes, respectively.
"The scanning tool also offers convenience," Budge said. "Many patients with swollen limbs often have great difficulty traveling from their homes to the clinic to have their measurements taken. The scanner should make it possible to take extremely accurate limb measurements in the patients' homes or villages, without cumbersome equipment or inconveniencing patients.
"To our knowledge, this is the first time that infrared 3-D scanning technology has been used in patients with filarial lymphedema," he added. "It worked so well that it has been added as a measurement tool in a future clinical trial in which we are collaborating."
That study is a two-year, multisite, international clinical trial to determine whether the antibiotic doxycycline can reduce the severity of swelling and disfigurement in patients with lymphatic filariasis. Enrollment for Washington University's partner site in Sri Lanka is scheduled to start this fall.
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