Evidence Based Medicine Made Dead Easy – Part I


Okay, so it will not be dead easy. We’ll see later the full list of tricks and obstacles we find when trying to deploy an evidence based medicine system in an EHR system in a later post. But hopefully this one will help you realize that data analysis modules can and should be installed alongside an EHR to make clinical research much more agile.

What’s EBM anyway?

According to Wikipedia (and, in turn, to Timmermann and Mauck) evidence-based medicine is about “apply[ing] the best available evidence gained from the scientific method to clinical decision making”. We all thought this was already true, given the amount of clinical magazines out there. However, evidence is not so easy to gather, and leaving out the doctor’s instinct out of the diagnosis is rarely a good idea. Now that EHRs are widespread, we at Brainific think that it is easy and convenient to deploy analysis systems that provide the kind of evidence EBM needs, and present it in a way that doctors can readily work with.

We will use PatientOS as the starting EHR on which to build our decision support demo. PatientOS follows the OpenEHR standard, an open specification for a health information model. An information model specification is more generic and flexible than a data model specification and more concerned about semantics. For these reasons, an information model tends to be more difficult to implement. All the data we handle in PatientOS falls in some Entry category, as specified in the OpenEHR architecture overview. OpenEHR is flexible enough to allow different processes on data, but it does not dig into the issue of how these data can be handled automatically. In our case, we would take Observations and Actions as inputs, and produce Assessments that will be reviewed by health professionals.

This series of posts will explain the use case, architecture, design and conclusions for a simple prototype, showing how a few open source products will allow us to quickly obtain evidence from our own clinical data.

The Scenario

Suppose we have already deployed PatientOS in our health center. We would like to relieve the statistician of so many doctors asking about simple tests, and instead have him focused on researching more robust and avanced ones. So we want our application to automatically retrieve the data the doctors need, and perform some standard test on it that the statistician will have already coded.

One such test will be whether one drug affects the patient’s weight after its prescription. We will use a Student t-test, where we will compare the difference in weight before and after the prescription for prescribed patients against the same measurements in a control group. The null hypothesis says that both groups will have zero difference, that is, that the mean in weight will be the same before and after the prescription. Note that there are thousands datasets in a clinical environment to which the Student t-test can be applied.

The statistician already knows how to code such a test. The IT staff can help him out with the code needed to interface the clinical data. We may use any data that follow its rules, so the statistician only needs to code the test once, and then the IT staff will access the data the doctors need in each specific case. Once the statistician has made its code available, exactly the same process can be applied to any specific dataset.

In turn, apart from all the billing, prescription and data record solutions, doctors may use a small window to interface this application and create a Student t-test. There they can select the data for each patient they want to analyze, as long as it is suitable for the test. The data of any patient can then be included in this experiment as soon as they come to the doctor’s office with a couple of clicks, so a new analysis can be done on the fly after enough new evidence has arrived. It can also be automated so that it runs in the background every nth patient, or even perform tests on other variables the doctor has not thought of, just in case.

The following post will illustrate how such a data analysis server would interface with the EHR system to retrieve the data and perform our statistical tests. We will perform a small proof of concept on a toy PatientOS installation including data collection from PatientOS and statistical analysis.

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