The BMI calculator is the NHS's flagship interactive tool. While adult BMI is a relatively simple calculation, the child BMI provided by this tool is based on a large statistical dataset and is delivered by a custom algorithm.
A child BMI result based on UK population data is only available via the NHS, as lead developer for Antbits Ltd I had the reponsibility of liasing with NHS statisticians, adapting their formulae and building and maintaining multiple iterations of this tool over a 10 year period.
Deploying interactive content to the NHS site was quite a challenge, everything had to be GOV.UK Design system compliant, WCAG 2.0 compliant, and keyboard navigable. The tool needed to be delivered inline with no use of iframes, able to resize itself while in use and be responsive to desktop and mobile environments.
The NHS uses Wagtail CMS as a back end, all the tools I produced with Antbits were submitted and tested via a pipeline on Azure then made available as modules within the CMS in multiple staging and production environments.
Antbits prototyped the design and UX aspects in Adobe XD, I then built and delivered the working tool. This included implementing the Child BMI and adult BMR algorithms, these only existed as VBA scripts in spreadsheets and relied on a non native JavaScript behaviour (normal distribution) which I was able to adapt from other languages.
We also integrated our own custom analytics tools, as well as various third party analytics systems required by the client. Editorial content was organized and delivered via a Google Sheets powered API of my own design.
All outputs then had to be ratified and signed off by medical professionals.
Due to internal policy changes NHS Digital has ceased using external contractors and as a result has retired or rebuilt all our original tools to run server side with decreased functionality. The demo below is the most recent iteration that I worked on.