Assessment Center API

The license and invoice are typically sent within about a week of receiving your licensee and billing details. After that, timing depends on how quickly payment is received, so paying by credit card or wire is recommended. The API download link is sent once payment is confirmed.

If these are two different data collection platforms with different purposes, these will require two instances of the API. Each API instance requires its own license.

The API license is a template used with all clients, and we have limited legal resources for making modifications. Minor edits are occasionally possible, but substantive legal changes can delay your license by many months. Note the Terms of Use included as an Exhibit are the same Terms of Use that are applicable across all uses of HealthMeasures and found on our website. The Terms of Use indicate that permission is required for electronic use of HealthMeasures; the API license gives you that permission.

Yes. A vendor may get a single institution license on behalf of one client.

The complete set of available English and Spanish measures for unlimited administration by an unlimited number of clinicians to an unlimited number of patients; annual API releases; multiple administration formats (computer adaptive tests , fixed form administration); and automatic scoring.

Check, wire/EFT, credit card (Visa, MasterCard, Discover).

The default license term is three years, beginning when the API is delivered to you. Other term lengths are available in one-year increments by request. Fees are paid in advance once a year, although you may pay for multiple years at once. After the first 12 months, you may terminate the license with 30 days’ written notice. At the end of the term, you may request a renewal for an additional term. Fees are locked in for the length of each term.

A significant advantage in using the API is the ability to administer measures in a computer adaptive tests (CATs) format so that each question is tailored to the respondent based on the previous response. CATs:

• Produce more precise scores with fewer questions.
• Reduce patient burden.
• Provide more power for detecting differences in scores.

Additional benefits of the API include:

• Automatic scoring that produces scores for all respondents, even those with missing data. Without the API, the scoring tables in the free, downloadable scoring manuals do not provide scores for respondents who have any missing item responses.
• Access to over 1,500 electronic measures without the need to individually program each measure manually from the PDF.
• Built-in score interpretation information for most PROMIS measures (e.g., thresholds that delineate mild/moderate/severe score categories).

We provide limited, virtual technical support with your IT team, but you will need IT resources to enable the API in your system.

The performance measures of the NIH Toolbox (e.g., Cognition tests) are not self-report measures like the other measures included in the API. The NIH Toolbox includes measures that contain puzzles and tasks that are inherently multi-modal (e.g., image and sound components). The scoring for the NIH Toolbox has been normed based on the specific timing and presentation that is used in the iPad app. However, many of the Emotion measures are included in the API.

Any measure that produces multiple scores, such as PROMIS Global Health or a profile measure, is considered a battery. Batteries can be viewed by clicking “List Batteries” in the API Demo. Guidance for calling a battery from the API is provided here. 

Note that “PROMIS-10” is a common nickname for the official measure, PROMIS Global Health. Be sure to use the official measure name in any publications or reports as described in the Publication Checklist. 

Measurement systems aside from HealthMeasures may be added to the API if they utilize the same IRT and CAT framework. Fees to load the measures into the API apply. Contact  help@healthmeasures.net for more information.

Each CAT uses specific rules for determining when to stop administering items. Details about these rules are described at CAT Variations. For most HealthMeasures CATs, the median number of items administered is 4. The default maximum number of items administered is 8 items for “recommended” measures and 12 items for most other measures; this can be changed in the calibration files by changing the value associated with maxItemCount.

On average, each PROMIS item has been shown to take 7 seconds to complete. 

Theta scores and T-scores are produced by the API. A linear transformation (multiply by 10 and add 50) is used to obtain T-scores from theta scores.

Yes. Additional information about using the API for scoring-only is found at API-Powered Scoring.

HealthMeasures are developed and scored psychometrically using item response theory (IRT). The CATs are dynamic and IRT-based.

The engine of the API includes the algorithms for administering and scoring the measures and is not available without a license. You must license the API if you would like access to the IRT parameters to input into your own CAT engine.

The HealthMeasures team is in Northwestern University’s Feinberg School of Medicine. The security and privacy of clients’ confidential data are important to Northwestern University. Northwestern University does not collect, process, or store data on behalf of API clients. The API is delivered to and hosted on the client’s server for use behind their firewall. Northwestern University’s information security policies are located here. Northwestern University HIPAA/ISO Information Security Guidance is located here. Additionally, the API is compliant with the 2018 European Commission Data Protection guidelines.

The API is sent to you to host on your own server behind your own firewall. Northwestern University does not process or receive any data from your use of the API. The security protections related to the API are the parameters of the system you are using with your own network and data collection platform.

The Assessment Center API is a RESTful web service. Technical teams experienced in working with a Microsoft stack (Windows Server and Microsoft SQL Server) typically test and implement the API within a couple weeks. Users typically consider this a simple process, and the API architect is available to answer any questions.

Yes. The individual item scores, theta scores, and T-scores are all accessible endpoints for storing in your own database. A discussion about each API endpoint can be found in the technical walk-through.

Yes. The API does not have a user interface; it only provides the measure content (question text) and algorithms for administering and scoring. The measures will appear however you have your data collection platform set up to display items. Company-specific branding and theming may be used so that API measures are seamless with other measures being administered to your patients.

Guidelines for how HealthMeasures should appear are included with your license. These include recommendations such as displaying one item per screen and showing the item context (e.g., “In the past 7 days) on a separate line from the stem (e.g., …”I felt uneasy.”). We also recommend that the items are presented with as little other text on the screen as possible to reduce cognitive burden for respondents.