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What ACR20, ACR50 and ACR70 means to you

I wrote this article several years ago. I wrote it to explain what the ACR numbers mean in the clinical research data about the drugs we are taking. These are the numbers that are bandied about to show that these drugs are worth using. These numbers are not complicated. Understanding them  will start demystifying what these drugs are all about.

Where will you find these numbers?  They are there in the fine print of the drug data sheet. AbbVie’s Humira,(adalimumab) website calls it ‘full prescribing information’ and has it located in the footer of their site.  Orencia includes the data sheet with its medication.

You should have one included with your medication. This is not the sheet that gives you reminders to follow your prescription as ordered. You can instantly identify it by its small print. The paper looks frail but it is quite sturdy. Starts small and opens quite large.  You can also google the data sheet for your medication. My Orencia data sheet was last revised in 2020.

Drug companies have clinical studies in order to have their drugs approved. Results of those studies are in the prescribing data sheet.

They use the terms ACR20, ACR50 and ACR70 to explain results of the studies.The time span is usually three months and six months  and sometime  twelve months.  The data for my Orencia doesn’t go beyond one year. Humira has two years in some of their studies. There are newer studies for Orencia.

This time I have been on Orencia for about nine months. For me it works on average about 50% with bursts up to 70% and lows to 0%. It has the lowest incidence of side effects and complications of the biologics.  The worst is severe infection.  It can also cause complications for those with COPD. It doesn’t seem to cause the cancer, heart disease or many of the other complications  that some biologics do.

ACR20 means 20% improvement  

ACR50 means 50% improvement

ACR70 means 70% improvement

So looking under the heading Inadequate response to methotrexate on my Orencia data sheet. The report finds the following.

ACR20   3 months                68%

ACR20   6 months                76%

So according to this data:

There is a 20% improvement for 68% of the subjects.

  • The improvement is 20%
  • The number of subjects having this relief at three months is 68% increasing to 76% at six months.

The claim that Orencia helps relief symptoms of RA is a valid one. When I am at my worst 20% improvement seems like a dream. However, after a while I long for more than a 20%. Let’s look at ACR50, which means 50% relief  for those who had inadequate relief from methotrexate.

ACR50  3 months                 33%

ACR50  6 months                 52%

There is a 50% improvement for 33% of the subjects.

  • The improvement is 50%.
  • The number of subjects having this relief at three months is 33% increasing to 52% at six months.

This level of improvement is meaningful. Having a 50% relief is livable. It is not good enough, but it is something to build on. Orencia plateaus at this level of relief for the year as other studies demonstrate.

Fewer subjects reach ACR70. However, there is a lucky group who did. About a   quarter of the subjects who are on Orencia will approach meaningful relief at six months.

ACR70  3 months                 13%

ACR70  6 months                 26%

There is a 70% improvement for 13% of the subjects

  • The improvement is 70%.
  • The number of subjects having this relief at three months is 13% increasing to 26% at six months. This improvement is considered clinically significant.

Many of the participants had some relief. At six months fifty percent of the group had 50% relief. The effectiveness plateaus at that rate through the end of a year. Only twenty-six percent of the entire group approached a relief we wanted and that was considered a clinically significant improvement. Humira and other biologics I looked at didn’t do any better.

The good thing is that Orencia offers relief from RA symptoms. The bad thing is that it doesn’t help most of us enough. It is a wonder drug for only 26% of us.


  1. Pingback: RA, Biologic Medication and the numbers | Mary's Arthritis

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