Whether conscious or not, almost every decision in medicine is based off a theorem of pre and post probability.

For instance, I order an abdominal ultrasound and paracentesis for the patient whom I suspect to have new onset ascites.

If their abdominal was tympanic and it did not have a wave, I might start thinking about a small bowel obstruction instead and thus not waste time with a paracentesis.

To keep me active in learning, I love making this decision conscious whenever possible.

It assists me in creating effective shared decision making with patients as well as with proper utilization of resources.

We reviewed the medical app diagnose back in January which helps physicians translate likelihood ratios into pre and post test probability and we will take a look at the medical app SnapDx in this review.

The opening screen of SnapDx is a list of around 55 diagnoses in alphabetical order. Once you click on a diagnosis (ascites in this example), a list of various rule in and rule out physical exam finding appear along with a toggle to set your pre-test probability. As you highlight a finding or lack thereof, the post test probability appears at the bottom of the screen highlighted in green for positive and red for negative.


The user interface is simple, yet effective. To continue with the example of ascites, I simply scroll to change my pre-test probability (50% in this example) and as you select exam findings the post test probability changes.



If you click the information button, the app takes you to a brief overview of the clinical diagnosis in question (above shows the information about the capacity exam) as well as information about the authors and sources. This is great added content and rounds out the user’s knowledge of the evidence nicely.

Evidence based medicine

  • Great citations for each diagnosis.

Healthcare providers that would benefit from the app

  • Medical students, mid-levels, residents and young physicians.
  • Price
    • $9.99
    • User friendly
    • Great evidence based medicin
  • Dislikes
    • Keep adding diagnoses
    • Organize the diagnoses by system for easier navigation possibly via a simple bar tool at the bottom (alphabetical, system based, etc).

  • Overall
    • A great tool for Bayes’ Theorem.
    • Increase the content as other apps such as diagnose offer similar quantity for a lower price.
    • As of publish, no Android version of the app is available.
  • Overall Score
  • User Interface

    Simple and clean with attention to detail

  • Multimedia Usage

    I would like to have folders or system organized diagnoses

  • Price

    When compared to other apps with similar functionality, this app is significantly more expensive

  • Real World Applicability

    I love making my unconscious thoughts conscious but this app needs more robust content before it earns a 4 or 5

  • Device Used For Review

    iPhone 5

  • Available for DownloadiPad