LABUN:
Welcome to the third of our short explainers for the Hunger Vital Sign. This episode will explain a bit more about what we mean when we say the Hunger Vital Sign is a valid screening tool. I’m your host, Helen Labun. And to help with the explanations, we have a guest expert from the organization that created the Hunger Vital Sign.
SHEWARD:
I'm Richard Sheward, Director of Innovative Partnerships at Children's HealthWatch
LABUN:
Here, we’re going to get into the details of how we can tell Hunger Vital Sign is giving us a good sense of whether a household is at risk of food insecurity and also whether that indicates a risk of poor health outcomes. And yes, this is statistics, so the word “good” there does have specific numbers and probability scores connected to it, which are in the papers linked in the show notes.
From the first episode, we know that Hunger Vital Sign began with a big advantage, because someone else, namely the U.S. Department of Agriculture, had already defined food insecurity and come up with a tool to measure it, a tool referred to by the acronym HFSS – household food security survey.
SHEWARD:
The way that the USDA HFSS is designed is that it measures the ready availability of nutritionally adequate and safe foods. What it measures is the sufficiency of household food as experienced by household members. It's not able to determine the nutritional adequacy of diets, which a nutritionist would be able to measure. And so it’s very much grounded in the household experience of whether or not they're able to attain the types of food that they desire in socially acceptable ways. And it's really grounded in economics and financial resources versus specifics of individual diets, per se.
LABUN:
Last episode we discussed how a screen is only a first step in a process, and this definition gives a hint at what some second steps might be. There’s bringing a household’s food up to a baseline of available, adequate food. But what if there are other concerns, like if children are already showing signs of underdevelopment or there’s a complicating illness -- in that instance we might bring in a nutritionist to help find the best diet to match those individual circumstances. Even within the USDA’s construct of basic adequacy linked to financial resources, a screen is still a first step. More steps are needed to determine something like eligibility for financial assistance through the USDA SNAP program.
SHEWARD:
SNAP is administered in a way that calculates eligibility in economic terms, in this case, as a percentage of the federal poverty line, as opposed to just simply whether or not an individual is food secure or food insecure. And so to qualify and enroll in SNAP eligibility is based on a number of income tests that must be met. Your gross monthly income must be in most cases out or below 130% of the poverty line. And your net income after certain deductions household income deductions are applied, must be out or below the poverty line. And then your assets must below fall below certain limits.
LABUN:
A properly built screening tool can lead into all of these possible pathways. But if you’re saving those detailed questions for future steps, you don’t want the initial screener to also be highly detailed. Detail is both the virtue and the downfall of the HFSS. That survey measures food insecurity across a continuum, starting with food security and detailing the gradations all the way through levels of food insecurity.
SHEWARD:
So the way that the USDA household food security survey module operates is on a scale and it measures food security as high food security, meaning that there are no reported indications of food, access problems, or limitations, or marginal food security, which are one or two indications, usually anxiety over the availability or the amount of food, or a shortage of food in the house, but no real indication of changes in one's diet or the amount of food intake. And then further on the scale, entering into low food security, we find changing not just the quantity of food, but also the quality and the variety and the desirability of one's diet. And then very low food security is when an individual reports multiple indications of disrupted eating patterns, including reduced food intake. And what we oftentimes see is, in the context of a household with children, that household level food insecurity is when you'll see parents shielding children from the reduction in food intake. And when we see families that are unable to provide that sort of shield, then that's when we enter into low, very low food security with child food insecurity, when children themselves are skipping meals and reducing both the quality of the food, but also the quantity.
LABUN:
This is important detail when you need detail, and in the show notes we’ll link more research built from the full food insecurity tool. For initial screening, the researchers wanted to shorten the survey as much as possible and still get very close to a correct undetailed positive / negative result on food insecurity. That’s the specificity and sensitivity from last episode. To be more precise, they wanted these attributes:
SHEWARD:
That it would have high sensitivity over 90%, that it would have high specificity over 80%.
LABUN:
That’s validity compared to the HFSS food insecurity definition. But the Hunger Vital Sign is meant to be more than just an abridged HFSS. It’s used in a medical setting to uncover invisible health risks, and so the researchers also need to check the connection to health outcomes for children and infants. One challenge in understanding this connection is that the poor health outcomes may not show up for decades – here again the researchers were able to pull from the existing research base, and their detailed surveys, to understand where to look for warning signals.
SHEWARD:
We often say at Children's HealthWatch that young children are the canaries in the coal mine, meaning that even though young children aren't going to develop those chronic health conditions that they might develop later on in life as adults resulting from experiencing repeated cyclical instances of food insecurity or other economic or households hardships, we do see that in children's reported health, satisfied caregivers, the rate of hospitalizations, their healthcare utilization patterns do show up in a relatively short time span. And we've seen how these indicators have changed as a result of changes in public policy, and even how the prevalence of food insecurity in our sentinel surveillance sample changes as a result of food in as a result of public policy changes.
LABUN:
I want to emphasize that last point. This group knew health-related indicators that serve as warnings for long-term impacts of food insecurity – they also knew what indicators are responsive to change without a long time lag. This is like a classic couples therapy issue – are you responding to a current relationship problem, or one that was true years ago but isn’t right now? There’s variability in food security status and corresponding health risks, too. Children’s HealthWatch saw positive effects from more generous public policies on food access during recovery from the 2008 recession, and negative ones when the policies returned to status quo. They’re monitoring the effects of expansions during COVID-19. We want to see this kind of responsiveness because it means the problem is, in fact, solvable. It’s just not easy and some of the problems are less data-driven and more political. As I said, it’s a bit like couples therapy.
SHEWARD:
The clinical indicators that we selected were based on years of research by the Children's HealthWatch team, understanding the risks and health outcomes associated with food insecurity in the case of very young children and caregivers living in the same household. Some of those conditions and outcomes that we've demonstrated in our research were, you know, children who were either underweight or, in extreme cases, diagnosed with failure to thrive. In some cases, overweight children that were screened at risk for developmental delays, children whose health was reported as fair or poor versus good or excellent. And then in the case of caregivers themselves we've demonstrated associations between food insecurity and self-reported health status of the caregiver as fair or poor compared to good or excellent, and positive screens for maternal depression and anxiety.
LABUN:
From this set-up, I’m now going to summarize a bunch of statistics. You’ll find the original paper in the show notes. The short version is this: The researchers had a list of variables for determining health outcomes, those items included hospitalizations, caregivers’ assessment of the child’s health, an existing tool to measure developmental risk . . . and also assessment for the caregivers’ physical and mental health. You can test sensitivity and specificity related to each variable. You can also take the group of key health outcome indicators and test whether that whole set of variables corresponds to food insecurity status, which it does, and whether the Hunger Vital Sign screen is a good predictor of those health outcomes, which it is. From that work, we can now say that the Hunger Vital Sign tool predicts food insecurity status, and the results correspond to a set of indicators that tell us a child is at risk for poor health outcomes.
In other words, this is a valid tool.
But how well do the results found in this original research reflect the results when the tools gets used in other places? By other screeners? And what happens if you want to move beyond children into screening other groups of patients?
These are all good questions. Keep listening for some answers.
The main ideas to take away from this episode are:
- The Hunger Vital Sign screening tool can signal for health care providers which patients are at risk of both food insecurity and poor health, including outcomes that might be years away.
- Hunger Vital Sign is not a detailed evaluation of a patient’s current food security status, the quality of their current diet, or their health status – that would require other diagnostic tools.
- By calibrating the original screen correctly, health care practices can connect patients to the appropriate people for this type of follow up – high sensitivity means that they aren’t missing patients who ought to screen positive, and high specificity means they aren’t referring on a lot of patients who do not need this level of additional follow up.
For resources connected to the topics covered in this episode, click on the link in the show notes. Next up in our series is information on how to create a reliable screening tool.