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What Is the Rheumatoid Arthritis Severity Scale?

Medically reviewed by Brenda B. Spriggs, MD, MPH, FACP on February 15, 2017Written by Elea Carey

Rheumatoid arthritis overview

Rheumatoid arthritis (RA) is a chronic and progressive disease. Understanding the severity of the disease is an important factor in helping you and your doctor evaluate if treatments are working, what treatments to consider next, and how to prevent progression and damage in the future.

The Rheumatoid Arthritis Severity Scale (RASS) was designed to help doctors determine disease activity, functional impairment, and physical damage caused by RA.

Diagnosis

RA causes the lining cells of your joints to become inflamed, resulting in swelling, stiffness, and pain. This inflammation involves the affected joints and the surrounding tissue, including tendon sheaths.

RA can sometimes be difficult to diagnose. This is because joint pain and fatigue are not specific to RA.

To diagnose RA, doctors rely on your medical history, a physical examination, blood tests, and X-rays of the hands and feet. Your doctor may refer you to a specialist, or rheumatologist, to confirm the diagnosis. Anyone who has persistent joint pain and swelling, without a diagnosis, should be referred to a rheumatologist.

Problems with old assessments

After diagnosis, the level and progression of RA need to be monitored and tracked. Prior to RASS, doctors combined results from a physical examination with factors reported by the patient, such as pain level, and inflammatory blood markers, to estimate RA severity.

Doctors also used the Health Assessment Questionnaire (HAQ), in which patients rated their own level of pain. Of course, everyone has a different threshold for pain, which can make these assessment models inaccurate. These assessment methods were also complicated by a close relationship between pain and depression.

The role of depression in assessment

Depression can be a significant component of RA. But there are challenges with using it to measure disease severity, including:

  • some patients may be more depressed than others
  • some patients may feel particularly depressed at the time of examination
  • some patients may not acknowledge they are depressed

While depression can be an element of RA, measuring it is not helpful for disease activity assessment. The RASS is completed by your doctor and based on the visible signs of the disease. It’s not based on your individual emotional assessment.

Types of RA

It’s important to know what type of RA you have to get an accurate assessment of disease activity. There are three types of RA:

  • rheumatoid factor positive (seropositive RA)
  • rheumatoid factor negative (seronegative RA)
  • juvenile RA (juvenile idiopathic arthritis)

What the RASS measures

The RASS measures three areas:

  • disease activity
  • functional impairment
  • physical damage

All three areas are assessed using a range of 1-100, with a score of 1 meaning there’s no evidence of the condition and 100 means the maximum level of progression.

Doctors look for disease activity like joint swelling during a physical exam. A doctor will also check for functional impairment with range-of-motion exercises. The physical damage component of the RASS looks at how much permanent damage RA has caused.

Disease activity score

The disease activity score (DAS) determines whether RA is in remission or whether there is low, moderate, or severe disease activity. This is perhaps the most important of the three scores for you to be familiar with.

Knowing your disease activity score will help you and your doctor assess if treatments are working or if they need to be changed.

Functional impairment

Following the DAS, the RASS looks at signals of functional impairment, or SOFI. Your doctor determines SOFI by looking at how far and how well you’re able to move your hands, arms (upper SOFI), and legs (lower SOFI). Your doctor will also look at how quickly you can walk a certain distance, either with or without assistive devices like a cane or walker.

Physical damage

The final part of the RASS looks at how much damage the disease has caused. This step is completed with an X-ray or other imaging tools, such as an MRI or a CT scan.

For the physical damage component, your doctor will look for scarring and destruction or deformity of the joints affected by RA and of the bones around them.

Understanding and treating RA

Diagnosing RA may not be easy because disease symptoms can be similar to many other conditions. Once the diagnosis is made, the severity of the disease needs to be determined in order to choose optimal treatment. An ongoing understanding of disease activity is critical to your health and well-being.

The RASS will help your doctor pinpoint the severity of your disease and the effectiveness of treatment.

Check out this RA Break It Down Video for an overview of the condition.

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