Limitations of YHF

The Your Heart Forecast tools were not made to substitute a proper, fully featured CVD Risk Assessment tool

We quite often find ourselves saying that the ‘Your Heart Forecast tool is a risk visualisation and communication tool, and not a fully fledged CVD Risk Assessment tool’. We’re trying to draw an important distinction between the two types of tool. Simply; it comes down to their intended purpose, and what they were designed for.

There are limitations which apply to the use of these tools. You can read more within the joint statement made by the tool creators here: YHF 2014 Joint Statements

What is a CVD Risk Assessment tool?

We would define a CVD Risk Assessment tool as a piece of software which implements the local guidelines and generates, for all patients, an appropriate CVD Risk score. This could be a 5 or a 10 year risk, this would depend on the locale and the guidelines which have been adopted. In New Zealand we use a Framingham based, 5 year calculation, and then vary from that base result given certain circumstances.

The variations include the following:

  • Applying upward adjusters (one off, singular upward adjustment of 5%) based on things like: 
    • ethnicity, 
    • family history of premature CVD in first degree relative,
    • diabetes of long duration (10 years or more), diabetes with elevated HbA1c level (64mmol/mol or more)
  • Assuming a ‘mimimum risk level of 15%’ – This means that if framingham delivered less than 15% the Risk value used for the check or management would be assumed to be ‘at least 15%’ based on:
    • Total Cholesterol of 8mmol/L or more.
    • TC:HDL ratio of 8 or more.
    • BP consistently 170/100 or more.
  • A ‘clinically high’ classification is applied (framingham is not used) for those patients who have already had previous CVD events, some genetic lipid disorders, Diabetes with nephropathy or Diabetes with other renal disease causing renal impairment. For these patients, the risk is known to be ‘somewhere above 20%’, exactly where has not yet been formally established.

What is the short-fall of the YHF tool vs a Risk Assessment tool?

The 5% upward adjustment (shown in green above) is handled within Your Heart Forecast however neither of the considerations shown in red are. This is because of the complexity involved in conveying these risk profiles using a graphed approach as neither of these two profiles are fully modifiable.

What do we mean by not-fully modifiable risk profiles? If you changed all of the normal considerations for that patient, yet fail to address the singular item which causes the ‘classification’ to be applied, then you will, according to the guidelines have no discerable effect on their risk profile. In the case of the clinical history driving a ‘clinically high’ classification you will not be able to calculate any difference as the formulas simply don’t allow for it.

So what?

Its for the above reasoning that a design decision was taken to exclude the red cases from use within the Your Heart Forecast tool. Instead these were handled by listing these cases as ‘exclusions’ within the first page of the tool. This requires the clinical user to read, understand and acknowledge that not all patients can be put through the Your Heart Forecast tool.

It appears that not all providers read everything given to them, and we’re concerned that unless this point of difference is stressed that these particular considerations may be over-looked.

The Your Heart Forecast tool was never intended to handle all potential risk cases, as you would expect a fully-functional risk assessment tool to, it was designed (and functions very well) to communicate risk to patients who have a fully-modifiable risk case.

So what should you use instead?

We have a number of products which were built for the more comprehensive Heart and Diabetes checks, for Primary Care, Secondary Care and also for Workplace based screenings. All of these (where appropriate [where it’s a fully modifiable risk profile]) feed directly into the Your Heart Forecast tool, in order to aid the communication of risk. Where it’s not appropriate to use the visualisation tool these simply return the risk level and encourage appropriate maangement (which is guided by these tools).

Predict CVD Diabetes is our flagship product in this area, it provides full and comprehensive clinical decision support for Heart and Diabetes checks along with the associated management advice for follow-up as and when the risks uncovered during these checks warrant it.


For more information on any of the above, please contact: sales@enigma.co.nz