App Review of DDx Teacher: Differential Diagnosis, History & Physical Aid

Between third year of medical school and intern year in residency a transition occurs from asking absolutely everything and doing non-directed physical exams to completing a focused review of systems and a goal directed physical exam. This transition can be difficult because in the beginning you ask seemingly random questions to come up with a diagnosis until experience teaches you to ask specific questions.

For example, in heart failure you might have asked about shortness of breath and chest pain but with time questions focus on change in orthopnea and whether baseline angina has become unstable.

To help me with this transition I used Diagnosaurus and to this day have recommended it to medical students who are struggling to think broadly about what a particular sign or set of symptoms might mean. My favorite book for this purpose was DeGowin’s diagnostic examination which not only offered broad differentials based on various signs and symptoms but also described how to perform various maneuvers as well.

DDx Teacher, created by the University of California at San Diego School of Medicine, is a commendable app that functions as both a differential diagnosis creator as well as guide for how to effectively use a review of symptoms to guide your diagnosis and exam. The more I have explored the app the more I respect its ingenuity.


The app opens to a list of systems (General, Eye, etc) and after a user selects an exam, a list of questions for each system appears. For each question there are further subsections, depending on the various findings one might encounter, guiding the user towards particular diagnoses. The easiest way to understand the app’s usefulness is a clinical example.


Brief Clinical Scenario

A third year medical student is asked to see a patient with a history of “heart disease” in clinic. Prior to entering the patient’s room he tries to refresh his memory of the basic questions he should ask. When he chooses cardiovascular he sees a list of 10 questions including prompts for “chronic cardiovascular disorders”, “chest pain”, “lower extremity edema”, and “wounds/ulcers in feet” among others. Under these subsections the question is explained. Associated with chronic cardiovascular disease is a list of important diagnoses; hypertension, congestive heart failure, and medications.


For lower extremity edema there is a prompt between unilateral or bilateral extremity and then a list with links for each (hydrostatic, low oncotic pressure, inflammatory).


When a diagnosis link is clicked (hydrostatic left-sided heart failure, for example) another paragraph of information is displayed which has specific diagnoses, physical exam findings, and well as etiology information (elevated JVP caused by CAD or Aortic stenosis, for example). This is a powerful tool to help drive on-the-spot learning.


One major improvement would be to convert existing hyperlinks into in-app information. In the picture shown above, when you click on the hyperlinks of physical exam findings (elevated JVP or edema, for examples) you are taken outside the application to a website with further information. It seems this website is the basis for this app, as well as a different free-standing application by the same developers. The application, Pocket PEx, covers the physical exam side of the website while DDx Teacher covers the differential diagnosis and review of symptoms portion of the website. If these apps were combined into one app the hyperlinks would be eliminated and the user would have an even more impressive amount of information available.

Evidence based medicine
Unfortunately there are no listed references. Even if there are not direct quotes it would be helpful to have a bibliography of books, websites, etc. that informed the application.

What providers would benefit from this App?
Residents, mid-levels and medical students

  • Price
    • 2.99
    • Fabulous point of care teaching on completing a thoughtful review of systems
    • Extremely in-depth differential diagnosis teaching
  • Dislikes
    • Although the web links work well they are inherently clunky. Many hospitals lack easy internet access within applications due to wireless restrictions, the links take time to open, and navigation on a small screen makes finding information challenging. I would rather the application take up more memory (by combining the two applications DDx Teacher and Pocket PEx) than resort to using links.
    • A basic search function (that links to section and sub-section headings for example) and favorites section would create more effective point of care use
    • Lack of evidence citations
  • Overall

    A surprisingly effective, in-depth, and functional point of care teaching tool for medical students. It enlivens the process of obtaining a review of systems and creating a differential diagnosis.

  • Overall Score
  • User Interface

    The app packs in a large amount of information and does not feel cluttered

  • Multimedia Usage

    I prefer in-app information whenever possible as links (even well made links) to information are cumbersome and almost always challenging to use

  • Price

    Well priced for the amount of information and functionality

  • Real World Applicability

    Extremely useful application

  • Device Used For Review

    iPhone 5

  • Available for DownloadiPhoneiPad