Outcomes assessment for intervention studies requires blinding of reviewers to prevent bias. We used Mozilla Firefox and the Greasemonkey Add-on to remove notes generated for intervention patients during a randomized controlled trial to ensure blinding during electronic chart review. Similar methods could be employed with other web-based electronic medical records.

1. The Greasemonkey Firefox Add-On for Altering Display of Data
in a Web-Based Electronic Medical Record
Allison B. McCoy, PhD 1
and Josh F. Peterson, MD, MPH2
1 School of Biomedical Informatics, The University of Texas Health Science Center at Houston, Houston, TX
2 Departments of Medicine and Biomedical Informatics, Vanderbilt University Medical Center, Nashville, TN
Greasemonkey Implementation Architecture
Objective Validation
To describe the use of the Greasemonkey Firefox Add-on We implemented the Greasemonkey script during a
to alter data display in a web-based electronic medical randomized controlled trial to evaluate pharmacy
record (EMR), hiding intervention status notes from surveillance for adverse drug events, where custom notes
blinded reviewers during a randomized controlled trial. existed only for intervention group patients. The script
successfully maintained blinding during outcomes
// ==UserScript== assessment by four reviewers throughout the study.
// @name Hide Notes
Greasemonkey // @namespace http://dbmi.mc.vanderbilt.edu/
// @include https://*.mc.vanderbilt.edu/cgi-bin/sp/*
// ==/UserScript==
Greasemonkey is a free, open-source extension for the
Mozilla Firefox web browser. Greasemonkey users can unsafeWindow.hideAKINotes = function() { Discussion
var s = document.getElementsByTagName('span');
install site-specific scripts, written in JavaScript, that for (i = 0; i < s.length; i++) { Many locally-developed and commercial EMRs are web-
Original Web Page Display if (s[i].getAttribute('styp') == 'Pharmacy Recommendation') {
manipulate site contents through the Document Object s[i].style.display="none"; based, and displays could be augmented using techniques
Model interface when a page loads. This method allows s[i].previousSibling.style.display="none";
} that we applied for reviewer blinding. Other applications
investigators to alter web-based displays without changing } might include interface customization for individual user
}
server-side code. preferences or experimental design evaluation.
var chart = document.getElementById('PC2');
if (chart != null) { For those systems not supported in Firefox, alternate
chart.addEventListener('load', function() {
var s = chart.contentDocument.getElementsByTagName('span'); software provides similar functionality for Internet Explorer,
Setting for (i = 0; i < s.length; i++) { Safari, and other browsers. The software must be installed
if (s[i].getAttribute('styp') == 'Pharmacy Recommendation') {
Vanderbilt University Medical Center utilizes a locally- Greasemonkey adds user specified s[i].style.display="none"; on each browser to be accessed by the user. Some
developed, web-based EMR, in which providers write and JavaScript to the web page. s[i].previousSibling.style.display="none";
knowledge of uniquely identifying element attributes or
}
view various patient notes. Developers can create custom inner HTML for content to be manipulated is necessary for
if (s[i].getAttribute('class') == 'Tab') {
note types, such as those generated by pharmacists var oc = s[i].getAttribute('oc').replace(/"/g, "'"); developers to create the user script.
s[i].setAttribute('oc', oc + '; hideAKINotes();');
through an electronic medication safety surveillance tool. }
}
} , false);
}
Conclusion
Script Description
The Greasemonkey Firefox Add-on effectively maintained
We developed a Greasemonkey script to locate and hide User Script blinding during a randomized controlled trial. Investigators
surveillance notes. The script first identifies HTML
utilizing web-based EMRs could employ similar methods to
elements with a surveillance notes type attribute. Next, the
ensure reviewer blinding during chart reviews or
script sets the element’s style display property to ‘none’,
manipulate user interfaces for other research objectives.
hiding the element. An event listener ensures repeats the
search and remove function if the chart is refreshed. Altered Web Page Display
The authors were funded by grants T15LM007450 and R01LM00965.