EBM Tools provides a simple app to calculate post test probability and related statistics

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Purpose of App Review

  • to review the robustness of the EBM Tools app
  • to review the applicability of the EBM Tools app

Introduction

In an ideal world, every test would be 100% sensitive and 100% specific. In the real world, though, nothing is 100%.  Healthcare providers must make important health-care decisions for their patients with less than perfect information. While many of these decisions are based on experience, it also helps to have statistical aids to guide decision making. The EBM Tools app seeks to provide this guidance via calculating post-test probability.

User Interface

When you open the app, you are brought to the Home screen, which is the only screen for the app.

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The screen is broken up into two portions. The top portion provides the results of calculations for post-test probability, as well as the positive and negative likelihood ratios.

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The bottom portion of the screen allows for user input in several areas. In order to make the calculations, the user must put in the result of the test, the sensitivity and specificity of the test, as well as the pretest probability. No references sensitivities and specificities are provided for various tests.

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The line bars then allow you to see how changing the test parameters changes the probabilities. For example, I am evaluating a patient for preterm labor and I am considering obtaining sending a fetal fibronectin (fFN) test. Based on the literature, I know that the sensitivity is 53% and the specificity is 89% for delivery prior to 34 weeks.

Based on my medical workup thus far, I think she has a 50% probability of being in preterm labor. Thus, I plug these numbers into the app. If the test comes back negative, the calculator tells me that the post-test probability of her being in preterm labor is only 34%, but is 83% if the test returns positive.

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If I change my pre-test probability to 27%, a positive test gives me a post-test probability of 65%.

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In my theoretic practice, I only treat patients for preterm labor if their post-test probability is greater than 70%. This calculator helps me decide how to treat my patient based on the test metrics and my concern for preterm labor.

Price

  • Free

Likes

  • simple interface
  • ability to change sensitivity, specificity, and pretest probability according to what you can find in the literature
  • use of line bars for input information

Dislikes

  • limited statistical calculations
  • one-screen only
  • does not give formulas for calculations
  • does not discuss what the various metrics mean and how they can/should be used

Healthcare providers that would benefit from the app

  • Healthcare providers and researchers needing a tool to calculate post-test probabilities. The app could potentially help decide whether a test is ordered or not, helping providers and patients to spend healthcare dollars where they will make the most difference.

Conclusions

  • EBM Tools is a statistically-restricted app–it provides the ability to calculate post-test probability. Though the name may be a misnomer in the array of EBM tools available, the post-test probability calculation is useful and the app is easy to use. It is available for the iPhone and iPad, but is not currently available on the Android platform.

iMedicalApps recommended?

  • Yes

iTunes Link

Rating: 3.5/5
1. User Interface – 5.  Easy interface with one screen and draggable linebars.
2. Multimedia usage – 2.  Uses split screen and real-time tracking.
3. Price – 5.  Free is fair.
4. Real world applicability – 2.  Helpful for demonstrating the effect of a particular test and deciding whether to order the test. Depends on how often the provider/researcher orders test.

App version: 1.0
Compatibility: iPhone 3GS, iPhone 4, iPhone 4S, iPhone 5, iPod touch (3rd generation), iPod touch (4th generation), iPod touch (5th generation) and iPad
Requires: Requires iOS 6.0 or later
Tested on: iPhone 4S

Disclaimer:
This post does not establish, nor is it intended to establish, a patient physician relationship with anyone. It does not substitute for professional advice, and does not substitute for an in-person evaluation with your healthcare provider. It does not provide the definitive statement on the subject addressed. Before using these apps please consult with your own physician or healthcare provider as to the apps validity and accuracy as this post is not intended to affirm the validity or accuracy of the apps in question. The app(s) mentioned in this post should not be used without discussing the app first with your healthcare provider.

Discussion ( 1 comment ) Post a Comment
  • Um, the werd “likelihood” is spelled wrung, in two different ways, no less! And givin that there is but a single screne for this app, and a grand totle of 20 words shown in the entire app, a developer should try not to spell fulley 10% of his/her words wrong!
    – JSt

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