Modified Severity-Weighted Assessment Tool (mSWAT)

Written by

Danica Uzelac, RN
Clinical Research and Photopheresis Programs Coordinator
Rush University Medical Center

What is the mSWAT?

The mSWAT (Modified Severity-Weighted Assessment Tool) is one of several tools a health care provider uses to monitor active cutaneous T-cell lymphoma (CTCL). CTCL research professionals most commonly use the mSWAT. If you participate in a clinical trial (also known as a research study), chances are your skin will be checked with this tool.

“Tools” sound scary. Fortunately, the mSWAT, and several other assessment tools, only require a provider to look at your skin. A provider may use a tool to complete a visual exam before you even notice.

History of the Severity-Weighted Assessment Tool

Before the mSWAT, a dermatology team developed the original SWAT (Severity-Weighted Assessment Tool). The dermatology researchers collected 12 years of data on 323 individual patients over 1186 visits. The SWAT required an additional seven years of analysis before publication in 2002. In total, SWAT development took 20 years.

To perform the SWAT, the provider inspected each individual patch, plaque, and tumor. Multipliers, also known as weighting factors, gave specific “weight” or “value” to each CTCL lesion type. Patches, which are flat, earned a multiplier of one. Plaques, which are raised, earned a multiplier of two. Tumors, which are larger and solid, earned a multiplier of three. Mathematically, a multiplier of three (tumor) contributed to a higher SWAT score than a multiplier of one or two.

The SWAT also utilized a technique known as grid-point counting. The provider used an overlay, or map, to count squares to determine each lesion’s size. Each individual patch size measurement was added with other patch measurements. Plaques and tumors underwent the same process.  Next, each patch, plaque, and tumor total was multiplied by the applicable weighting factor. In the last step of the SWAT, the total in each of the three categories of lesions was added to obtain a final score.  

The SWAT result was a number that a provider monitored over time. A stable number suggested a stable condition. A lower number suggested less active CTCL and conversely, a higher number suggested more active CTCL.

The modified SWAT: Body Surface Area

The “m” in mSWAT means “modified” or changed from the original. Today’s mSWAT increases the tumor weighting factor from a three to a four and eliminates the grid-point counting. Instead, the provider uses body surface area (BSA) in 12 body areas to calculate skin involvement. BSA measures the percent of the body with patches, plaques, and tumors. Look at column two in the example below, titled “% BSA in Body Region”. The 12 body areas are described along with the value assigned to each area. According to the mSWAT, the head represents 7% BSA. The thighs (front and back) represent 19% BSA. Entire body involvement results in 100% BSA. Accordingly, 0% BSA represents clear skin.

Has your provider ever asked to see your hand?

Although there are several simple methods available to calculate the BSA, the mSWAT uses the palm plus fingers method. This method equates 1% BSA to the individual patient’s palm plus fingers. The provider needs a good look at the patient’s hand to use this tool. In the example below, the head size equates to seven of an individual’s palm plus fingers. The neck size equates to two of an individual’s palm plus fingers and so on down the list.

An assessment example

(View larger image of example)

With such a complex tool, it can be helpful to look at an example. The example depicts the mSWAT of patient A. Patient A has two CTCL patches, 1% BSA each. According to the 1% definition, each patch is equivalent in size to patient A’s palm plus fingers. One patch is on the upper arm and the other is on the foot. On the stomach, or anterior trunk, there is one plaque, 2% BSA, equivalent to two palms plus fingers. On the forearm, there is a tumor, 0.5% BSA, half patient A’s palm plus fingers. The columns are added and then multiplied by the assigned weighting factor. In this example, the mSWAT result is 8, the three columns’ summation.

The same provider should perform the mSWAT every time.

There are differences in how each provider performs this assessment. If you move from one doctor’s office to another, expect a different mSWAT result, even if your CTCL remains the same.

Some healthcare providers find the mSWAT too difficult to use in routine CTCL care. Instead, many providers choose BSA alone to monitor skin. To get an accurate CTCL picture over months and years, the selected tool and method must remain the same.

Is there an app for that?

Yes! A clinical team at St. John’s Institute of Dermatology in London, England developed the Cutaneous Lymphoma Resource Tools, also known as the CL-App. The CL-App allows a provider to easily input data and quickly calculate a mSWAT result.

Patients often feel overwhelmed when trying to understand medical terminology. Patients diagnosed with a rare disease may find this especially true. Be kind to yourself. It’s a whole new language. Remember that you have partners in this journey. Reach out to your healthcare providers. Reach out to your family and friends. And of course, the Cutaneous Lymphoma Foundation is always here to support you.

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