Why the rules keep changing
APS affects about 5 out of every 100,000 people each year. Many go undiagnosed for years. The symptoms can look like other conditions. And the tests are not perfect.
The first set of rules came out in 1999. These were called the Sapporo criteria. Doctors updated them in 2006. Then again in 2023.
Each update aimed to fix problems with the old rules. But no one had ever compared all three directly in a large study.
That is what this new research did. It looked at data from 2,214 APS patients and nearly 4,000 other people. The goal was simple. Find out which set of rules catches the most cases without making mistakes.
The trade-off no one talks about
Here is the challenge with any diagnostic test. You can design it to catch more cases. But then you will also misdiagnose some healthy people. Or you can make it very strict. But then you will miss some real cases.
This is called the balance between sensitivity and specificity.
Sensitivity means how good a test is at finding people who actually have the disease. Specificity means how good it is at ruling out people who do not.
The 2006 rules were good at sensitivity. They caught 86 out of 100 real APS cases. But they were less specific. They sometimes said someone had APS when they did not.
The 2023 rules flipped this. They were extremely specific. They correctly ruled out 98 out of 100 healthy people. But they missed more real cases.
The 2023 criteria caught 20 percent fewer cases than the 2006 version.
How the study worked
Researchers gathered data from seven studies around the world. They used a method called network meta-analysis. This is a fancy way of saying they combined results from multiple studies to get a clearer picture.
They compared all three sets of criteria. The 1999 Sapporo rules. The 2006 revised rules. And the 2023 ACR/EULAR rules.
The 1999 rules did not perform well. They had the lowest accuracy overall. Most doctors have already stopped using them.
The real debate was between the 2006 and 2023 versions.
The 2006 rules caught 86 percent of APS cases. The 2023 rules caught fewer. But the 2023 rules were much better at avoiding false alarms.
For a patient, this matters a lot.
If you have clear, textbook symptoms of APS, the 2023 rules will likely confirm your diagnosis with high confidence. You can trust that result.
If your symptoms are less clear, the 2023 rules might miss you. You could have APS but be told you do not.
The 2006 rules are better at catching these unclear cases. But they also label some healthy people as having APS.
Where this leaves patients
So which set of rules should doctors use?
The study authors suggest a middle path. Use the 2023 rules for research studies and for patients with unusual symptoms. The high specificity means fewer false positives. This is important when testing new treatments or studying the disease.
Use the 2006 rules when you want to catch as many cases as possible. This is better for everyday clinical care.
There is a catch. No set of rules is perfect. And the study had limits. Only seven studies met the criteria for inclusion. That is a small number. More research is needed.
Also, the study looked at classification criteria. These are designed for research, not for diagnosing individual patients. Doctors use them as guides, not as strict rules.
What happens next
Researchers are already working on better ways to diagnose APS. New blood tests are being developed. Some look for different antibodies. Others use newer technology to find signs of the disease.
The 2023 rules may get updated again as more evidence comes in. For now, the message is clear. If you have symptoms of APS, make sure your doctor knows about both sets of criteria. Ask which one they are using and why.
The right diagnosis depends on using the right tool for your specific situation.