How long have I got? Take a blood test.

Would you take a blood test that accurately predicts your chance of dying within five years?

This may surprise you, but doctors are notoriously bad at answering the question, "How much time have I got left?" Turns out there are blood tests that just might be more accurate than your GP, says a study just published in the Canadian Medical Association Journal.

Inflammation is the body's way of fighting off an infection like pneumonia. That's the good kind of inflammation. What you may not know is that inflammation can also track the development and progression of cancer, heart attacks, strokes, rheumatoid arthritis, type 2 diabetes, Crohn's disease, and many other serious conditions. That's the bad kind of inflammation.  

Good or bad, we can measure inflammation with blood tests that have names like interleukin-6 (IL-6), C-reactive protein (CRP) and alpha1-acid glycoprotein (AGP). Together, they're called inflammatory biomarkers. The higher the level, the more severe the disease. 

Researchers from France and the United Kingdom studied more than 6500 men and women ages 45 to 69. They were able to measure these three inflammatory biomarker tests (IL-6, CRP and AGP) from blood samples collected between 1997 and 1999. They followed the subjects of the study until June 2015. Of the 6500 present at the beginning of the study, 736 died; 181 from heart disease or stroke, and 347 from cancer.  

An elevated AGP, IL-6 and CRP predicted an increased risk of dying within five years of the blood test being taken. As a test, IL-6 and CRP performed better than AGP. After the first five years, only IL-6 predicted an increased chance of dying over the long haul. The bottom line is that IL-6 is a better predictor of dying in the short and long term.

There are short and long term implications of this sort of testing. Short term, these tests are already in fairly wide use.  A commentary that was published along with the research study (sorry, the commentary is behind a paywall) said that heart specialists are using these inflammatory biomarkers to screen patients at risk of heart attacks. Recently, they've begun using this sort of testing for doctors to decide what if any kind of cholesterol-lowering drug to prescribe. Right now, the testing is not being used much as a tool for screening patients for cancer, nor are doctors using these tests yet to advise patients on their short term and long term risk of dying.  But that'll come in time. 

When done by recognized laboratories, the testing is reliable. InsideTracker and Wellness FX offer direct to consumer testing of biomarkers. The big issue is not the test results but the interpretation of test results. The author of the commentary in CMAJ says there are many unanswered questions regarding the value of the testing – even for experts.

Critics of consumer testing services like InsideTracker say they lack context, and may lead to additional testing and treatment that is unnecessary.  More serious are concerns that naturopaths and other practitioners of complementary alternative medicine use this kind of testing to justify the prescribing of naturopathic remedies and nutraceuticals to treat chronic diseases by lowering inflammatory biomarkers to normal levels.

So, what should health consumers do?  These are very early days in the testing of inflammatory biomarkers.  We can learn whether a patient with cancer or heart disease has an elevated IL-6 or CRP.  What we don't know is whether treatments that bring those blood tests back to normal by reducing inflammation have any effect on the severity and the chance of dying of cancer or heart disease. Several clinical trials are currently looking at whether low dosages of drugs like methotrexate and colchicine – used to treat rheumatoid arthritis and gout – can reduce heart attacks by treating inflammation.

I can't blame consumers for wanting to take control of their health.  But right now, the interpretation of the testing is uncertain. Anyone who says otherwise should be doubted.