Frequently Asked Questions about DXplain

1. What is DXplain
DXplain is one of the most widely used computer-assisted decision support systems. DXplain can be used in two main modes. In the role of a medical textbook, DXplain can provide a comprehensive description and selected references for over 2,200 different diseases, emphasizing the signs and symptoms that occur in each disease, the etiology, the pathology, and the prognosis. DXplain can also list a differential diagnosis for any of approximately 4900 clinical findings.

In "case analysis mode" DXplain uses an interactive format to collect clinical information and produces a ranked list of diagnoses each of which could explain some or all of the clinical manifestations entered. DXplain can provide justification for each disease listed by displaying which of the case findings support a disease, can suggest what further clinical information would be useful to collect to support the presence of a specific disease and can list what clinical manifestations, if any, would make a specific disease less likely.

2. How long has DXplain been in use?
Development of DXplain began in 1984, and the initial version with information on approximately 500 diseases was released in 1986. National distribution of DXplain with a database of approximately 2000 diseases began in 1987 over the dial-up AMANET. After AMANET ceased operation in 1990, DXplain continued to be distributed over dial-up networks until 1995. Between 1991 and 1996 we also distributed DXplain as a stand-alone version that could be loaded on an individual PC. Since 1996, Internet access to the web-based version of DXplain replaced all previous methods of distribution.

3. What information is in the DXplain database?
The current DXplain knowledge base (KB) includes over 2300 diseases and over 4900 clinical findings (symptoms, signs, epidemiologic data and laboratory, endoscopic and radiologic findings). The average disease description includes 53 findings (with a range of from 10 to over 100). Each disease/finding pair has two numbers describing the relationship, one representing the frequency with which the finding occurs in the disease and the other the degree to which the presence of the finding suggests consideration of the disease. There are over 230,000 individual data points in the KB representing disease/finding relationships. In addition, each finding has an associated disease-independent importance attribute from 1 to 5 indicating how important it is to explain the presence of the finding. Each disease also has two associated values: one that is a crude approximation of its prevalence (very common, common, rare or very rare) and the other of its importance, ranked between 1 and 5, and intended to reflect the impact of not considering the disease if it is present.

4. How do I enter clinical findings?
DXplain will accept a wide variety of clinical data, including demographics, patient history information (symptoms), physical exam findings, laboratory test results and a variety of specialized tests such as radiological, echo, ECG and endoscopy findings. Just type one or more findings into the textbox, separated by a comma or a semi-colon and click Submit. You do not need to have any specialized training to use DXplain. There are useful HINTs on each screen.

5. What if I can't think of a DXplain finding or use the wrong word?
No problem. DXplain has extensive synonym matching capabilities, and is also forgiving of misspellings. DXplain may suggest more or less specific findings as options to the finding you enter.

6. Can DXplain help me select clinical findings to enter?
After you have entered your initial findings and produced a list of diagnoses, at each point in the case analysis mode, DXplain will offer a set of findings, which you can select as being present, absent, or unknown. These findings are selected on the basis of being potentially useful in refining the differential diagnosis.

7. What if one or two findings are very important to my case, and the others are less important?
DXplain offers a 'Focus' feature. After entering your case findings, click the checkboxes of the crucial finding(s) and then click on the Focus button. DXplain will present only those diseases in which the FOCUSed finding(s) are known to occur.

8. How can I find out more about a disease on the list of diseases presented?
Highlight the disease by clicking on it. Then click on the 'Dx Description' button to retrieve both a description of the disease AND a selected list of references.

9. I see a disease on the list, but don't understand why DXplain included it. Can I find out why?
Absolutely. Highlight the disease by clicking on it. Then click on the 'Evidence for Dx' button to see which entered findings support the disease, which important findings entered are not known to be part of the disease, and which other findings, if present, would support the disease. Any of these other findings can be added easily to your case description by clicking a checkbox.

10. What if a patient has known disease(s)?
You can enter common diseases such as diabetes and DXplain will use this information as another “finding.”

11. How about travel or occupational exposure?
You can enter relevant information about foreign travel and/or occupation, as well as medication use, since this information is included in the appropriate disease profiles.

12. What about regional differences?
DXplain can take into account the patient’s geographical location. This data can be entered if you feel it is relevant by including the appropriate geographic term as a patient finding. Thus, if the patient is from (or has traveled) to the American southwest, or in northern Europe, or in Africa, you can enter this fact as part of the patient description.

13. What are the red 'I's next to some finding names?
These indicate that the finding has other information associated with it, such as an explanation of the finding or a graphic image. If you click on the 'I' you will be shown this information.

14. What if I think DXplain made incorrect interpretations or suggestions?
From the beginning, we have incorporated user feedback as an easy option. We very much want to hear from users, both positive and negative feedback and suggestions for changes. User input about adding diseases or editing findings has been an important source of improvements over the years.

15. How do I access DXplain?
DXplain was created and is supported by the Laboratory of Computer Science of the Department of Medicine, Massachusetts General Hospital, Boston 02114. Medical schools, health care organizations and other educational institutions can access DXplain after signing a license agreement with Massachusetts General Hospital - see for details. There is a modest yearly royalty fee (dependent on the size of the organization) for unlimited access to each organization. At the present time, we do not support access to individuals.