Research & Insights

By Dole Oleson, March 21, 2013

Discovering Drug Side Effects with Crowdsourcing

As a recovering biology major, one of my favorite applications of crowdsourcing is solving public health problems. So far at CrowdFlower, we’ve enlisted the crowd to kill TB cells, count neurons in mouse cortices, and track epidemics. With some of the new tools we’ve built in the last year, I’d like to add tracking drug adverse events in social media to the list.

The Experiment:

We collected all tweets (on Twitter) that contained “Claritin” for the month of October 2012. After some basic filtering for spam tweets offering to sell Viagra with allergy medication, we were left with 4,900 tweets.

 

Next we looked to adverseevents.com for Claritin’s top 10 most common adverse events. The top 10 adverse events are from the FDA Adverse Event Reporting System (FAERS), which collects mandatory adverse event reports from drug manufacturers, and voluntary reports from medical professionals and consumers. Remember the Vioxx and fen-phen recalls? These drugs were withdrawn due to safety concerns as a result of Serious Adverse Events (SAEs) that were reported to the FDA through FAERS.

The Results:

We used our sentiment analysis product, Senti, to have our crowd review the 4,900 tweets and classify them for relevance, sentiment, author’s gender, and any of the top 10 most common adverse events as reported to the FDA. You can explore the data by clicking on the interactive graph below.



Interactive Senti Dashboard of one month of Claritin Adverse Events on Twitter
built with d3.js and crossfilter

We found 295 instances of adverse events in the top 10 categories on Twitter – a number higher than is reported to the FDA. In the last 12 months for which data is reported (Jul2012-Jun2012, data is only available through June 2012 at time of writing), there has been an average of 8 adverse events where Claritin was the primary suspect in reports to the FDA, and 265 total adverse events per month where Claritin was mentioned to the FDA in conjunction with other drugs. Almost all of the cases we found on Twitter were primarily due to Claritin, over 30X the number of primary events that are reported to the FDA.

Adverse Event Twitter FDA – PR* FDA – TR**
Dizziness 11 0 16
Convulsions 0 1 6
Heart Palpitations 5 0 7
Shortness of Breathe 4 0 19
Headaches 7 0 16
Drug Effect Decreased 66 0 3
Allergies Worse After Taking Drug 132 0 8
Bad Interaction Between Claritin And Another Drug 40 0 5
Nausea 4 0 19
Insomnia 26 0 9
Other 0 7 157
Total 295 8 265
Twitter adverse events are for October, 2012; FDA’s are rolling 12 month average
*Primary Reports **Total Reports

Over six percent of tweets mention an adverse event. The most common complaint is Claritin’s notorious failure rate. It’s not surprising that more serious adverse events (convulsions, heart palpitations, shortness of breathe) – are underrepresented in social media while comparatively minor effects (decreased drug efficacy, allergies worse, nausea) are overrepresented on Twitter relative to FDA reports.

Serious health problems are much more likely to be reported through traditional medical channels as opposed to social media. However, many lower impact effects – drug not working, allergies worse, bad interactions between Claritin and other drugs – may be deemed too minor to be reported through traditional medical channels and show up on Twitter in greater volume.

Percentages by Gender
Source Women Men
Total Tweets that contain “Claritin” 62% 48%
Tweets w/Adverse Events on Twitter 65% 35%
Adverse Events Reported to FDA 65% 35%

The two genders seem to tweet about Claritin in roughly equal proportion to stated adverse events for FDA – with women making up the majority of adverse events sufferers by almost a 2:1 margin. Women mention more serious conditions (heart palpitations, shortness of breathe, headaches) while men do not. Its unclear if this is because women are more likely to suffer from those conditions, are more likely to tweet about them, or that the sample size is too small to glean anything meaningful.

What It Means:

There is an order of magnitude more data on adverse events available on Twitter than the FDA receives – providing a much more expansive and inclusive dataset for adverse events. With the ability to find many more adverse events than are currently found, social media could provide an early warning detection system for postmarket surveillance of drugs, providing a safer environment for both consumers and pharmaceutical companies. There’s incredibly rich data out there, if you’re willing to look for it.