4 May 2016:
Given how different Lupus can be for each person, and how little is known about its triggers, you may have guessed that diagnosing Lupus is very hard to do. Warning: this is probably my most scientific-technical-language-y post of the month. (But my medic/scientist friends might be fascinated!)
There is no single blood test (or any other kind of test) that can conclusively demonstrate the presence of Lupus. Instead, a combination of many different blood test results, taken over time, sometimes combined with specific clinical presentations (such as kidney failure or discoid skin rash) are all taken into consideration when reaching a diagnosis. The Lupus Foundation of America says the average length of time to obtain a diagnosis is 6 years.
90% of people with Lupus will have a positive anti-nuclear antibody (ANA) test, but 10% of people with other autoimmune disorders will also have a positive ANA. Combine + ANA with a positive anti-DNA antibody test, and you conclusively have Lupus– but only 30% of people with Lupus have positive anti-DNA antibodies. In the UK much more than in the US, the erythrocyte sedimentation rate (ESR) is used to measure disease activity– but a raised ESR can also demonstrate activity of other diseases like Rheumatoid Arthritis and Crohn’s. Furthermore, some doctors use the occurrence of a check-list of symptoms, needing 4 out of possible 11, to diagnose Lupus, but other doctors don’t hold with that. So it’s possible for one doctor to decide there’s enough information to make a diagnosis of Lupus, and another doctor with the same information to conclude that there isn’t yet a conclusive demonstration of the presence of Lupus.
I was diagnosed when, after years of sometimes having a positive ANA and sometimes not, my GP in the States decided to test me for the anti-Smith antibody. Only found in 20% of people with Lupus, it is nonetheless a conclusive demonstration of the presence of Lupus, when combined with the ANA test, because it basically only occurs in people with with Lupus. However, this test is extremely unknown– in fact, in researching this post, the only website that even discusses the existence of the anti-Sm test is the Johns Hopkins Lupus Centre. Sorry this has been such a long one!! There’s no simple way to explain how Lupus is diagnosed, because there’s no way simple way to diagnose Lupus!
Not much has changed around diagnosing Lupus in the last four years. There is on-going research, though most of it is on hold at the moment. I personally suspect that Lupus will ultimately turn out to have been an umbrella diagnosis for a plurality of sub-disorders, all autoimmune, which science will gradually pick apart and deal with each in their own way.
Wondering what’s going on with these posts? Check out my explanation HERE!
This Isolation Life 