Let's see if we can get some test coverage.

I suggest using jest and enzyme.

https://jestjs.io/

https://airbnb.io/enzyme/

There are several concepts in the app that seem like good candidates to be defined as constants such as hospitalMortality, risk, care, and decafScore.

It would be helpful to define them as const somewhere, and use them throughout the app instead of having their definitions show up as part of conditional logic.

There may be a map (data structure) you can use to represent some of these relationships that could help clean up some of the code:

{
  1: {
    hospitalMortality: '...',
    risk: '...',
    care: '...'
  },
  ...
}

Again, probably need some iteration on this concept before it fits this use case

It might not be necessary to always wait for a click on the calculate button in order to perform a calculation.

Can you think of a way that would enable the calculator to react to any form input, and return a calculation? (as long as they are all set)

package.json is sufficient to define external dependancies without having to commit the actual source of those dependencies to your repo.

(This is in contrast to pod files that are sometimes committed with iOS projects where dependency version management is a bit less stable)

Do you mind changing the name of this repo to something other than wellsheet?

My suggestion: decaf-risk-calculator

There are a few form-input button-like components that all look and behave really simliarly:
ExtendedMrc
Eosinopenia
ChestXray
AtrialFibrilation
Acidemia

Can you think of a way to consolidate them into a single, re-useable component?

A call signature like

<ToggleButton
    title={'Eosinopenia'}
    options={eosinopeniaOptions}
    onSelect={() => this.onSelectEosinopenia}>

could take you a long way (will probably need to iterate on this).