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THE agonising wait to discover whether a baby has cystic fibrosis could soon
be a thing of the past. A small portable detector developed by researchers in
Ireland can give a result in minutes, rather than the full day needed for a lab
test.

Among Caucasians, about 1 in 2500 contracts cystic fibrosis. It wrecks vital
organs, including the lungs and pancreas, by clogging them with thick, sticky
mucus. Few sufferers live beyond the age of 30. Doctors can detect the disease
by looking for the genes that cause it, but a much more common check is the
“sweat test”. Cystic fibrosis boosts levels of sodium and chloride ions in
sweat, which are easier to detect.

“The sweat test is the gold standard,” says Dermot Diamond, associate
director of the National Centre for Sensor Research at Dublin City University.
The test still takes time, however, and considerable expertise. Samples of sweat
must be sent to a central laboratory for analysis. The process can take up to a
day.

Diamond and his team used off-the-shelf components to build a quick and
easy-to-use system for detecting cystic fibrosis. A unit that looks like a
wristwatch uses an electric field to push the chemical pilocarpine nitrate into
the skin. This dilates the pores and sweat is then sucked up and stored in a
duct in the watch.

The researchers then dilute the sweat and pump it through a commercial sensor
commonly used for blood analysis. The sensor records the levels of sodium,
chloride and potassium ions. A laptop computer analyses this data and gives an
instant diagnosis. The whole process takes about 30 minutes. “A quick diagnosis
like that would be very useful,” says Jim Littlewood, an adviser to Britain’s
Cystic Fibrosis Trust.

The new design examines the same sample simultaneously for all salts, unlike
the conventional sweat test, in which the sample is divided up and analysed
separately for sodium and chloride.

In tests using 21 samples, which included sweat from known cystic fibrosis
sufferers and controls, the device diagnosed all but two of the samples
correctly. Tests on the same samples using conventional methods gave the same
misdiagnosis, suggesting these were borderline cases, the researchers say. “You
have the potential to get a very robust measurement. You have very few false
positives and negatives,” says Diamond. Unfortunately, the pilocarpine nitrate
that stimulates sweating interferes with chloride detection. Redesigning the
chloride-sensing electrode would solve the problem.

Diamond says the sweat collector and sensor could be integrated into the
watch. A radio transmitter could then beam the data to a computer, which would
diagnose the condition.

The device would have many uses other than diagnosis. “It’s something you
could wear, for example, when exercising. You could be analysing a number of
parameters in the sweat, for sports science and for general health,” he says.