WASHINGTON — Every year, millions of Americans will go to their doctors complaining of pain, and their doctors will ask them to rate their degree of discomfort on a zero-to-10 scale, or using a range of smiley-face symbols.

The doctor will have to take their word for it. And then, all too often, the doctor will prescribe a powerful and addictive opioid painkiller. 

It's a longstanding — if imprecise and subjective — way of measuring and treating pain. And it's at least partly responsible for starting an opioid addiction crisis that killed 64,000 people last year. 

"One of the things we heard from many physicians is that the pain-specific indicator contributed to this crisis," said White House Counselor Kellyanne Conway, President Trump's top adviser on the opioid crisis.

"We don’t think health care by emoji is good idea," she said.

So the Trump administration, which has declared the opioid crisis a public health emergency, is backing efforts to find better ways of measuring and treating pain in the hope of developing precise treatments that would be more effective than opioids — and without the often catastrophic side effects.

Next month, the National Institutes of Health will open proposals for $4 million in small business grants to develop a device or technology to objectively measure pain. That could take the form of a blood test, a device to measure pupil dilation, or software to interpret facial expressions.

NIH Director Francis Collins calls it the "pain-o-meter."

It's not entirely clear what the pain-o-meter would look like, or exactly how it would work. It hasn't been invented — yet. 

But the pain-o-meter isn't meant to be the end game. It's actually the first step in understanding the measurable indicators — or "biomarkers" — that can indicate pain. And that, in turn, could pinpoint causes and treatments, bringing precision medicine to pain management.

"There is this issue about whether we'll ever really get where we want to go in terms of developing effective pain management if we just consider pain to be one thing," Collins told the National Advisory Council for Complementary and Integrative Health last month. "Because we know that it's not." 

The current tools of measuring pain don't take into account individual pain thresholds, which can be influenced by genetics, past experiences and other conditions. They often don't distinguish different causes of pain, or different pain sensations. 

To understand how a pain-o-meter could lead to advances in preventing opioid abuse, it's important to understand how the opioid crisis began two decades ago.

In 1995, the American Pain Society began to promote the idea that pain was "the fifth vital sign" — after temperature, pulse, respiration and blood pressure. Health care professionals were encouraged to actively monitor patients' pain. But unlike the other vital signs, pain could only be measured by asking.

Then in 1996, as more patients began to report pain, Purdue Pharmaceuticals introduced Oxycontin, a time-release formulation that it said could kill pain with the power of an opioid but less danger of addiction.

Twenty years later, the overuse of prescription painkillers has grown into a national epidemic of opioid addiction that now includes heroin and its deadly synthetic cousin, fentanyl. Various federal surveys suggest how how that evolution took place: 

► About 38% of U.S. adults have taken a prescription painkiller in the past year. 

► About half of people over 12 who misused prescription painkillers said they obtained the pills for free from a friend or a relative. 

► An estimated 4% to 6% who misuse prescription opioids transition will transition to heroin, often because they no longer have access to prescription painkillers. 

► About 80% of people who use heroin started out by misusing prescription opioids.

Conway says that's what's different about this epidemic: It often starts in a household medicine cabinet. 

"Over-prescribing has been problematic, as has the default notion that pain management means pain medicine. That is not true of everyone," she said.

Eliminating trial-and-error

The final report of President Trump's opioid commission identified a number of factors that contributed to the crisis. The pharmaceutical industry aggressively marketed opioids to doctors. Health insurance policies favor opioids over other painkillers and non-medicinal treatments like acupuncture. Hospital patient satisfaction ratings often higher when patients are prescribed opioids. 

But also, they work. 

Opioids are cheap. They act quickly. And they take a lot of the guesswork out of trying to diagnose and treat pain. 

"We think of them as painkillers, but they don’t quote-unquote 'kill' all pain," said Dr. Sean Mackey, chief of pain medicine at the Stanford University Medical Center. "They often have a very short-term, immediate response that helps a large number of people."

Other pain treatments, he said, are the result of a "very long and time-consuming and frustrating trial of treatment after treatment."

"It’s literally trial and error," he said. "I'm pretty decent at it, and I bat about .400 in getting it right the first time. If you’re a baseball player and batting .400, you're making millions. If you’re a physician, you're not bragging about that."

With opioids, many doctors were batting 1.000.

Part of the problem, Mackey explains, is that doctors have no reliable way of predicting how any particular patient will respond to painkillers.

"Wouldn’t it be great if we had a way of determining who was going to run into problems with opioids?" he said. "That’s where this ties into the opioid epidemic."

Mackey sees the Trump administration's research into pain and addiction as a logical outgrowth of President Barack Obama's Precision Medicine Initiative — using the power of big data to help develop targeted treatments to diseases like cancer or Alzheimer’s.

But that pain data won't exist unless scientists find a way to effectively measure it. 

"In the olden days, people use to think that things like pain were outside the scope of scientific inquiry. It was in your head. It was subjective. But pain is real, your brain changes, your body changes," said Dr. Dave Thomas, who manages NIH's pain and opioid research efforts.

"To conduct science, you have to have good measurements," he said. "If you were trying to study chemistry and try to determine reactions based on heat, would you stick your finger in the beaker to see how hot it was?"

But even as scientists work to develop the pain-o-meter, they've voiced concerns about how to use it ethically. Until the science of pain is better understood, it would be a mistake to assume that every patient's pain can be measured in the same way, they said.

"How do you know that a patient who comes to you saying he has severe pain asking for an opioid — how do you know he is not feigning?" said Dr. Nora Volkow, the director of NIH's National Institute on Drug Abuse. "That's one of the concerns that has been voiced by the public."

And indeed, that's one possible use of the pain-o-meter — and a potentially a promising tool in combating opioid abuse. But it's not what most excites pain researchers. 

"I have had that argument, that it would be used for people who are claiming they're in pain for workman's comp, or try to get drugs. That's not my intent," said NIH's Thomas. "You could use a lie detector, come to think of it, and you’d have better precision than any pain-o-meter."

"I'm not a big fan of the pain-o-meter," said Mackey, whose research into pain has led to some of the biggest advancements in the technology. "The vast majority of my patients are not lying to me. They’re not trying to cheat to get opioids." 

For years, Mackey has tried to tamp down expectations for objective pain measurement. He's still not ready to use his research to testify in court that someone is or isn't experiencing pain, for example.

"I want to put the appropriate cautionary messages out there, that this is going to take a lot of hard science to do this right," he said.

But now he says he's more optimistic than ever. "If you would have asked me in 2007, I would have said we wouldn’t be able to do this. I think 10 years from now, we’re going to have something really cool."

The opioid crisis is a top priority for NIH, but there's more urgency behind ways to better save the lives and treat people already addicted: opioid reversal agents (and auto-injectors that can sense when someone has overdosed), medication-assisted treatments for addiction, and longer-term addiction treatments.  

"Those projects that can bring solutions right away are getting priority because we don’t have the luxury of time," said Volkow. On projects like the pain-o-meter, "We cannot put the same emphasis, even though they may be more transformative," she said.