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Unreported Side Effects of Drugs Are Found Using Internet Search Data, Study Finds
By JOHN MARKOFF
Using
data drawn from queries entered into Google, Microsoft and Yahoo search
engines, scientists at Microsoft, Stanford and Columbia University have
for the first time been able to detect evidence of unreported
prescription drug side effects before they were found by the Food and
Drug Administration?s warning system.
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 Using
automated software tools to examine queries by six million Internet
users taken from Web search logs in 2010, the researchers looked for
searches relating to an antidepressant, paroxetine, and a cholesterol
lowering drug, pravastatin. They were able to find evidence that the
combination of the two drugs caused high blood sugar.
The study,
which was reported in the Journal of the American Medical Informatics
Association on Wednesday, is based on data-mining techniques similar to
those employed by services like Google Flu Trends, which has been used
to give early warning of the prevalence of the sickness to the public.
The
F.D.A. asks physicians to report side effects through a system known as
the Adverse Event Reporting System. But its scope is limited by the
fact that data is generated only when a physician notices something and
reports it.
The new approach is a refinement of work done by the
laboratory of Russ B. Altman, the chairman of the Stanford
bioengineering department. The group had explored whether it was
possible to automate the process of discovering ?drug-drug? interactions
by using software to hunt through the data found in F.D.A. reports.
The
group reported in May 2011 that it was able to detect the interaction
between paroxetine and pravastatin in this way. Its research determined
that the patient?s risk of developing hyperglycemia was increased
compared with taking either drug individually.
The new study was
undertaken after Dr. Altman wondered whether there was a more immediate
and more accurate way to gain access to data similar to what the F.D.A.
had access to.
He turned to computer scientists at Microsoft, who
created software for scanning anonymized data collected from a software
toolbar installed in Web browsers by users who permitted their search
histories to be collected. The scientists were able to explore 82
million individual searches for drug, symptom and condition information.
The
researchers first identified individual searches for the terms
paroxetine and pravastatin, as well as searches for both terms, in 2010.
They then computed the likelihood that users in each group would also
search for hyperglycemia as well as roughly 80 of its symptoms ? words
or phrases like ?high blood sugar? or ?blurry vision.?
They
determined that people who searched for both drugs during the 12-month
period were significantly more likely to search for terms related to
hyperglycemia than were those who searched for just one of the drugs.
(About 10 percent, compared with 5 percent and 4 percent for just one
drug.)
They also found that people who did the searches for
symptoms relating to both drugs were likely to do the searches in a
short time period: 30 percent did the search on the same day, 40 percent
during the same week and 50 percent during the same month.
?You
can imagine how this kind of combination would be very, very hard to
study given all the different drug pairs or combinations that are out
there,? said Eric Horvitz, a managing co-director of Microsoft
Research?s laboratory in Redmond, Wash.
The researchers said they
were surprised by the strength of the ?signal? that they detected in
the searches and argued that it would be a valuable tool for the F.D.A.
to add to its current system for tracking adverse effects. ?There is a
potential public health benefit in listening to such signals,? they
wrote in the paper, ?and integrating them with other sources of
information.?
The researchers said that they were now thinking
about how to add new sources of information, like behavioral data and
information from social media sources. The challenge, they noted, was to
integrate new sources of data while protecting individual privacy.
Currently
the F.D.A. has financed the Sentinel Initiative, an effort begun in
2008 to assess the risks of drugs already on the market. Eventually,
that project plans to monitor drug use by as many as 100 million people
in the United States. The system will be based on information collected
by health care providers on a massive scale.
?I think there are
tons of drug-drug interactions ? that?s the bad news,? Dr. Altman said.
?The good news is we also have ways to evaluate the public health
impact.
?This is why I?m excited about F.D.A. involvement here.
They do have mechanisms and ways to pick up the things that we find and
triage them based on anticipated public health impact.?