Quantifiable measures make treat-to-target viable for PsA
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Though sometimes complex, treat-to-target strategies for psoriatic arthritis can lead to lower symptom states, better physical functionality and less structural damage to joints, according to Philip Mease, MD, a clinical professor at the University of Washington School of Medicine and Director of rheumatology research at the Swedish Medical Center in Seattle.
"We discovered that patients really appreciated being in that state from a symptom and function point of view, but it also correlated with long term gains such as less likelihood of structural damage progressing,” Mease said.
The treat-to-target approach initially emerged several years ago to treat diseases such as diabetes and rheumatoid arthritis and aimed to prioritize remission and/or low disease activity as target goals. More recently, the approach has been applied to psoriatic arthritis.
“It really started in rheumatology with rheumatoid arthritis, where we would identify a threshold of remission or low disease activity as a target to shoot for so we could evaluate the patient when they came in the office; evaluate their tender or swollen joints,” Mease said.
“We have adopted the same paradigm in setting our goals of treatment for psoriatic arthritis and are discovering the same things: that patients really appreciate being in a low symptom state and a better functional state. The correlation of that is they are going to have less structural damage to their joints, and have fewer problems down the road,” he said.
Stringent disease targets are set and closely monitored, requiring patients to visit their doctor frequently to evaluate whether they have met a pre-determined treatment goal. If not, their medications are adjusted, and more aggressive therapy is used until treatment goals are met regularly.
The key to formulating treatment targets for psoriatic arthritis is the recognition that the disease is more than just arthritis, Mease said.
“There is also, certainly, skin to be considered, which is an important clinical domain for patients: the degree of psoriasis. There are other factors too, including enthesitis, or sometimes the patient may have spondylitis," Mease said.
Quantifiable measures
There are now quantifiable measures that have been adopted and are usable in clinical trials and in clinical practice that make the treat-to-target approach viable for psoriatic arthritis, Mease said.
One of them is called the minimal disease activity criteria, which was developed by the GRAPPA Association.
The items that constitute the minimal disease activity criteria include an assessment of 68 joints for tenderness and 66 for swelling. An assessment of skin disease is done using the psoriasis area and severity index, and pain and patient global are rated on a numerical rating scale.
"This is actually a very easy thing to do in the clinic and one can accomplish this in just a couple of minutes with the patient," Mease said.
If the patient has achieved five of the following seven thresholds, then they are in a state of minimal disease activity.
- Less than or equal to one tender joint;
- Less than or equal to one swollen joint;
- Psoriasis Area and Severity Index of less than or equal to 1 or a psoriasis body surface area of less than 3%;
- An enthesitis assessment of less than or equal to one tender area of enthesial insertion;
- Health Assessment Questionnaire score less than or equal to 0.5;
- Patient global activity VAS less than or equal to 20; and
- Patient pain Visual Analogue Scale score less than or equal to 15.
If the patient has achieved all seven of these items, then they are in a very low state of disease activity equivalent to remission, according to Mease.
"I don't think there's any patient who wouldn't benefit from such an algorithm," Mease said. “The treat-to-target quantification really gives us some more accurate and reliable, quantified measures to try to achieve and that this is really the way to go to get to the state of remission.”
Low disease state and remission
It is acceptable to not reach remission, according to Mease. For example, if the clinician intensifies treatment to the extent that the patient begins to experience side effects such as more frequent infections, or in the case of some of the oral medications, abnormal liver function test, then it is wise to scale back the intensity of the treatment, Mease said.
“We have found that getting to a state of low disease activity is adequate; you don't have to get to remission," he said.
The biggest challenge of the treat-to-target approach is the time dedication it requires.
"A busy practitioner may not have the time to really reliably and carefully assess each of the important clinical domains," Mease said.
"On the other hand, it is very practical, and you can do it quickly. The patients really appreciate it, and it helps build trust," he said.
What to discuss with the patient
“I emphasize to them that we are very interested in assessing the full array of [psoriatic arthritis] features that they may display,” Mease said.
But there are some features that the patient may bring up that are not included in any of the objectifiable measures, such as inflammation induced fatigue, according to Mease.
“It is important to convey to the patient that if they have features like fatigue, or as another example, Achilles enthesitis, then that needs to really come to the fore in our discussion,” he said.
"This is the kind of thing where we want to ask patients, 'are there any other problems, like a particular function that you don't or can't do?," he said.
Disparities in care
Access to treat-to-target care is a significant issue, Mease said. If the patient has poor insurance, has no insurance, or their insurance program is very restricted, then they may not be able to get access to treatment that would be optimal for them.
"Many of the pharmaceutical companies bringing forward new medications are trying the best they can to reduce these problems of economic access by making their drugs more accessible, either by programs for low-income patients, or other ways in which they we try to get therapies for our patients," he said.
Another disparity is that some clinicians may not be adequately educated about the importance of treating to target, and do not employ a treat to target strategy for their patients, Mease said.
Next steps
Clinical trials of new medications are increasingly evaluating key secondary outcomes, after the typical primary ACR 20 or 50 outcome measures, Mease reported.
“This key secondary outcome is, ‘have you achieved minimal disease activity, or very low disease activity, or gaps in remission?’” Mease said.
“We are seeing an evidence base for new therapies that are being tested to achieve these thresholds, and physicians are able then to evaluate the quality effect of new medications,” he said.
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