Credit: fizkes/iStock
Credit: fizkes/iStock

You may think of yourself as living with a chronic condition such as Crohn’s disease. But to a global network of health care professionals, insurance companies, researchers, and electronic medical record systems, your condition also goes by a certain code — in this case, K50.90.

Called International Classification of Diseases (ICD) codes, these sets of letters and numbers are maintained by the World Health Organization (WHO), which most recently released its 10th version, called ICD-10, back in 2015. In the United States, the U.S. Centers for Medicare and Medicaid Services (CMS) and National Center for Health Statistics (NCHS) are in charge of overseeing ICD codes.

While coding may seem like backend gibberish, it has a critical impact on your everyday health care and the overall study of your medical conditions.

Either patients don’t know much about ICD codes at all, or “patients tend to throw up their hands at codes because codes are confusing or they don’t know how codes are used,” says Rick Gundling, Senior Vice President of Healthcare Financial Practices for the Healthcare Financial Management Association (HFMA).

Having at least a basic understanding of coding is important, he adds, especially for those living with chronic disease.

“Patients with chronic illnesses come into contact more often with billing, so coding impacts their out-of-pocket costs and insurance. And if there’s an error, it keeps getting repeated because they see that physician or hospital repeatedly,” says Gundling.

Where Do ICD Codes Come From?

ICD codes play a huge role in your health care — even if you’re not aware of it. If you go to the doctor and are diagnosed with osteoarthritis, for example, your provider puts all your information in your electronic medical record, including your condition expressed as an ICD code.

When choosing the appropriate code for you, your provider — or a professional coder at your doctor’s office or hospital — may consider a number of factors, including whether your condition is chronic or acute, its etiology (your condition’s origin), and the part of your body affected. With an osteoarthritis diagnosis, for example, this is a sampling of the ICD-10 options your health care provider can choose from to represent you:

  • Osteoarthritis primary – M15.0
  • Osteoarthritis bilateral, hip – M16.0
  • Osteoarthritis unilateral, hip – M16.1_ (1,2)
  • Osteoarthritis bilateral, knee – M17.0
  • Osteoarthritis unilateral, knee – M17.1_ (1,2)
  • Osteoarthritis bilateral, first carpometacarpal joint – M18.0
  • Osteoarthritis unilateral, first carpometacarpal joint – M18.1_ (1,2)

Once chosen, that diagnosis code doesn’t exist by itself. It has to make sense in connection with whatever separate treatment codes your doctor may choose for you. Your treatment is represented as a Current Procedural Terminology (CPT) code, which covers procedures and services, such as a knee replacement, or “arthroplasty, knee, condyle and plateau; medial OR lateral compartment” (27446).

While no one expects you to memorize all these coding specifics, it’s worthwhile to be aware of the basics.

“I wouldn’t put the burden on a patient to understand the technicalities,” says Dena Bravata, MD, Chief Medical Officer for Castlight Health, a cost transparency company. “But being aware of how your health care gets coded helps you understand what you might expect in terms of a bill. These codes are also important because they form your medical records and history.”

Gundling of the HFMA agrees. “How a condition is coded could impact how much something gets covered, how often a certain procedure can be done, and whether a certain procedure can be done,” he explains.

Timothy Laing, MD, Associate Professor of Rheumatology at Michigan Medicine, advises at least knowing the codes on the active “problem list” in your electronic medical record. “If you’re a patient and you have a given condition, it’s important to know how your physicians are classifying your disorder,” he says. “There’s a place where the doctor is supposed to put down your active medical problems and knowing what’s there could mean the difference between getting a test or medication paid for.”

Who Uses ICD Codes?

In short, everybody.

“The purpose of ICD-10 is to create a dictionary of diagnostic terms that everyone can agree on around the world,” says Dr. Laing. “Those terms are then used by people who do clinical research, by insurance companies who determine benefits, and by governments who want to understand health care.”

Here are the biggest players who are using ICD codes to determine your medical bills and understand your disease:

Insurance Companies

From your doctor’s office, your ICD codes travel to your insurance company as part of the bill that is submitted for reimbursement. This is where your diagnosis codes are considered alongside your treatment codes to make sure everything adds up.

“You may be denied access to a treatment or test based on the disease in your record,” says Dr. Laing. “CMS [Medicare and Medicaid] and private insurers don’t want to reimburse an MRI for an itchy elbow.” Medications are often approved by the U.S. Food and Drug Administration (FDA) based on certain indications linked to a specific condition, Dr. Laing explains.

If your indication is coded properly in your chart it’s often much easier to get payment for that treatment or medication than if you don’t have the appropriate code.

There are other ways that codes can misalign. “There might be an ICD-10 code that only applies to men, so if it’s mistakenly applied to a woman the insurance could be denied without a patient understanding why,” Gundling says.

There are also examples of medical conditions that do not have their own ICD code. Consider the case of a rheumatic condition called non-radiographic axial spondyloarthritis (nr-axSpA).

Non-radiographic axial spondyloarthritis is a form of inflammatory arthritis that falls under the umbrella of axial spondyloarthritis (axSpA). AxSpa encompasses two conditions that cause similar symptoms (such as back, buttock, and hip pain) but are diagnosed differently.

  • Ankylosing spondylitis (AS) causes inflammatory back pain and you can see damage to the spine or sacroiliac joints (where the spine connects to the pelvis) that is visible on X-rays.
  • Non-radiographic axial spondyloarthritis causes similar symptoms, but without damage that you can see on X-rays.

Until October 2020, nr-axSpA did not have its own ICD code — it’s now M46.80 — so patients who had nr-axSpA had to be lumped together in the same ICD code as ankylosing spondylitis in order to get diagnosed and receive treatment. This drastically limited the availability of information about the true prevalence of nr-axSpA and also impacted patients’ ability to receive proper treatment — and, importantly, start feeling better.

 Researchers and Scientists

The reach of ICD-10 codes is so broad that it impacts not just your medical records, but the entire field of study related to your condition. Once your codes — and the codes of other patients — are submitted for reimbursement, they become part of a hugely rich data set that researchers can mine to better understand the epidemiology of disease.

“Reviewing claims data can create lots of information for clinical researchers to study,” says Dr. Laing, who shares an example. Say a researcher wants to understand more about ankylosing spondylitis (AS), which is more common in northern than southern latitudes. The researcher may approach CMS and ask for all AS claims submitted over the last three years and do a zip code analysis to investigate that geographic association.

Another example: “There’s a lot of info to suggest that exposure to tobacco is a risk factor for rheumatoid arthritis,” Dr. Laing adds. “If you look into that connection by using claims data that includes ICD codes for smoking, you could confirm or deny that hypothesis. There’s lots of information that could be pulled out of data like that.”

(You can see, then, that when a condition doesn’t even have its own medical code, as non-radiographic axial spondyloarthritis lacked for so long, that it can affect an entire body of research on that medical condition.)

Code data can also assess practice variation, which means looking at different doctors who are treating the same condition differently, says Gundling. “A researcher may notice that RA patients who come to a particular practice undergo certain procedures less often but still have great outcomes.” It then becomes possible to ask what that practice may be doing that’s so effective.

Such insights can further our understanding of treatment approaches, risk factors, and other aspects of a condition, potentially improving care for anyone with that diagnosis.

How Do Changes to ICD Codes Affect Those with Chronic Illness?

Far from set in stone, ICD codes are periodically modified to reflect new thinking in science and health care. The ninth version (ICD-9 codes) contained about 14,000 diagnosis codes, which weren’t enough to keep up with advances in medicine. When the 10th version was adopted in 2015, it contained nearly 70,000 codes, representing conditions with greater specificity.

“The U.S. has been using ICD-9-CM since 1979, and it is not sufficiently robust to serve the health care needs of the future. The content is no longer clinically accurate and has limited data about patients’ medical conditions,” according to materials published by the U.S. Centers for Disease Control and Prevention (CDC) when the ICD-10 rolled out in 2015. What’s more, most of the world’s developed countries had already moved on to ICD-10, hampering the United States’ ability to compare diagnosis data on an international level.

One specialty that was significantly impacted by the explosion of codes was rheumatology.

“With the upgrade from ICD-9 to ICD-10, one of the important areas that popped up was rheumatology because the ICD-10 codes got much more precise,” says Caitlin Donovan, Senior Director of Public Relations for the National Patient Advocate Foundation. “Instead of just a general code, the new codes were specific to anatomy and other factors. It allows more precision, which enables researchers to look at a cohort of data and come up with more precise conclusions. And on a patient level it allows for less back and forth between providers and insurance companies.”

For example, ICD-9 described rheumatoid arthritis with the code 714.0. When ICD-10 came along, providers had a much wider menu of options to represent RA in a particular patient, such as:

  • 411: Rheumatoid myopathy with rheumatoid arthritis of right shoulder
  • 521: Rheumatoid polyneuropathy with rheumatoid arthritis of right elbow
  • 731: Rheumatoid arthritis with rheumatoid factor of right wrist without organ or systems involvement

But even ICD-10 can’t keep up with changes in medicine. ICD-11 codes are expected to come into effect on January 1, 2022.

Between these periodic system-wide overhauls, the ICD codes remain fluid to accommodate changes in science and health care. For example, as of January 1, 2021, the new ICD code for “personal history of COVID-19” is Z86.16.

The Impact of ICD Code Errors

“There can be all kinds of human errors and alphanumeric issues — someone can always make a mistake when entering something in a computer,” says Dr. Bravata. “Let’s say someone erroneously coded you as having a heart condition, that error gets propagated through your medical record and can get difficult to eradicate. So a little messy handwriting that gets coded the wrong way can perpetuate itself.”

While patients don’t normally have direct interaction with medical coding, ICD codes may be a place to start if you suspect a medical billing mistake.

“If your insurance isn’t covering something in the way you expected, consider saying to your physician’s office, ‘My insurance kicked this back, is the coding as accurate as it could be?’” advises Gundling. “Your insurance company just works off whatever code is sent to them from the doctor’s office, so make sure you’re getting all the coverage you’re owed. Sometimes you think it’s a problem with the payment, but it could be a problem with a code that determines the payment.”

Where Can You Find Your ICD Codes?

Given their importance, ICD codes must be easy for patients to find in their own bills, explanation of benefits (EOB), and electronic medical records (EMR), right?

“ICD-10 codes aren’t housed in one consistent place in the EMR. They’re not even typically in the EOB or the original bill. You’d have to request an itemized bill to see the codes,” says Donovan. “The EMR may list ICD-10 codes in the office notes, but that information isn’t always accessible in the patient portals.”

Patient paperwork that does include codes may not always list them as “ICD.” They may instead be listed under “DX” for diagnosis code, Gundling adds.

However, there is potential for improved access. “We hope that advances in EMRs will make it easier for patients to access their codes, along with all sorts of other information. Unfortunately, right now there’s no consistency in one system to another,” says Donovan.

This educational resource was made possible with support from UCB, a global biopharmaceutical company focused on neurology and immunology.

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