Part III: Understanding how to Develop Applications with HealthVault

Microsoft's HealthVault is not a "PHR" but rather a "PHR platform" with a set of back-end services for secure storage, retrieval and sharing of healthcare information. These services can be used by a developer to actually build what we may describe as a "classic PHR".

What does HealtVautlt mean to me as a developer? How does it work?
Here is the scenario as I see it, which explains how a developer may start to think of ways to use HealthVault:

Developing with HealthVault
- Lets assume a patient, John Doe registers for a HealthVault account. This is where his healthcare data would be stored. John Doe controls access to this data using his "Windows Live ID" credentials (user-name and password).

- Now suppose, I as a developer create a new PHR product called "Acme PHR" using HealthVault on the backend. That is, I develop the presentation layer, the actual website with my company's logo etc. I decide the look and feel of the application and the type of data I want want to collect and store for a patient. Additionally, I would also develop the business layer containing the business rules, knowledge-base and decision support functionality.

The final Acme PHR product is my company's application. The application performs the functions that I want it to perform. I can do interesting things with the application by combining the data in HealthVault with additional data that I define and store separately on my own server/database.

Designing a new HealthVault-based application- Personal Diet Planner and PHR
What do I mean by combining HealthVault data with my own defined data? Lets take an example. Suppose I want my PHR application to have the ability to provide different diets for patients with various health conditions, like diabetes, hypertension or obesity.

With my PHR, I will want to collect patient data such as weight, blood pressure, health conditions, blood sugar values, cholesterol results etc. This data is patient specific, so I decide to use HealthVault as the storage mechanism. Besides the convenience of using HealthVault's APIs, the big advantage of HealthVault is that it handles all the security issues, such as authorization and role based access to data (specified by the patient).

The database of the different diet plans however is stored on my company's servers. It is my company's proprietary data and would be kept entirely separate from HealthVault's data.

With my application, I can combine patient specific data from HealthVault, with my database of diet plans. So if a patient using my PHR, has high blood pressure and is obese, I may recommend a particular diet plan, while someone with just mild obesity, may get another diet recommendation. This is my application's "secret sauce", the ability to decide the proper diet for specific health conditions.

This is an important point, because my application is not about the details of storage and retrieval of health data, but rather, on how I use this patient's specific data and combine it with other data to create new innovative personal healthcare applications. This is much like an operating system. HealthVault essentially acts as an operating system like Windows, handling all the low level detail and chores, while my application focuses on the big picture.

Whats next? More Applications using common HealthVault Data
So patient John Doe uses my "Acme PHR" (with the special diet plan feature), and has entered his health data. John Doe is very happy with my PHR product.
But now, another company creates another product using HealthVault which recommends exercise plans for patients with specific health conditions. John Doe likes this idea. He has all his data already entered via my PHR product and is happy with the diet plan. He now wants exercise recommendations. John Doe can subscribe to this new "Exercise Planner" application. Fortunately, because it too uses HealthVault, John's data is already entered. This data can now be used by this new application. So using John Doe's existing weight, blood pressure and health condition data, an exercise plan can be recommended by this new product. There can be other products which do other things. The possibilities are endless.

HealthVault is like an Operating System
You can see the tremendous advantage of having personal health data stored once, with the ability to use it in multiple ways with disparate products. Just as the Windows operating system has resulted in countless software products, HealthVault likewise may lead to countless health care applications.