Explaing the 'e' in eGFR

What’s with this GFR test? For years there we were, medical professionals, just doing our jobs when out of nowhere comes a ‘new’ test we suddenly have to become knowledgeable of. It’s like we’re the only child whose parents have come home with a brand new baby sibling that we’re suddenly suppose to instantly love and accept. We didn’t ask for it, and things were fine until it came along to cause a lot of uncomfortable questions.
Hopefully this entry will answer questions about this newest diagnostic test.
First of all, GFR stands for Glomerular Filtration Rate. The glomerulus is the structure in the kidney responsible for filtering blood, so determine how well it is working can be used to measure kidney function.
Second of all, it’s not a new test. It’s actually a number calculated from a formula using four variables; plasma creatinine, age, gender and race.
Thirdly, the GFR derived from this formula is actually an estimated GFR . That’s why some labs report it as eGFR. Performing an actual GFR requires injecting a patient with a nuclear isotope (125I-iothalamate) and determining how long it takes for the kidneys to filter it out of the body. This is a procedure that cannot be performed on a large scale to screen patients who are at risk of developing chronic Kidney Disease (CKD).
In 1989 the National Institute of Diabetes and Digestion and Kidney Disease in the U.S. performed a study to see what affect diet could have on CKD and two of the tests used were plasma creatinine and 125I-iothalamate GFR.
As a result, a lot of useful data was produced, allowing researchers to develop a formula to quickly estimate GFR. The result was a magic number of 60 ml/minute/1.73 m^2. As long as the eGFR was 61 or greater, than the risk of CKD was decreased. A eGFR of 60 or less indicated further investigation.
Actually then, all the eGFR does is take the plasma creatinine and present is as a number to indicate kidney function.
But here are some ground rules for using the eGFR.
It cannot be used for paediatric patients eighteen years and under cannot have an eGFR performed on them. The test is gender specific. African Americans have a higher content of muscle, requiring a different formula than non African Americans.
Plasma creatinine must be used. Values from Point of care analyzers measuring creatinine using whole blood cannot use this formula.
In fact, any analyzer that measures plasma creatinine to calculate eGFR has to be standardized. What does that mean?
Finally, any analyzer that measures plasma creatinine has to be standardized. What does that mean?
The purpose of the eGFR is to screen patients at risk of developing CKD. However, if the analyzer being used has a high degree of variability , there is the potential for the patient having a wide range of results. One day your patient could have kidney disease with a eGFR of 58, the next day they could be a healthy 62.
An example of a successful standardization program is the one launched by the province of B.C. in 2003. It provided labs with specimens of known creatinine values for them to analyze. These labs then sent the results to the province, which calculated a correction factor for the analyzer.
The results speak for themselves.
Before the standardization program labs on average were reporting eGFR values 16.5% lower than they actually were. This meant that 535,000 British Columbians had been falsely diagnosed being at risk of developing kidney disease. By having labs use the correction factor in their formula for calculating eGFR, 449,000 patients were prevented from being misdiagnosed. Needless anxiety for the patient was avoided as well as the cost savings. The standardization program cost $335,000 to launch, and has a yearly budget of $135,000. Part of that goes towards educating physicians, patients and allied health professionals on the strengths and weaknesses of the eGFR as a diagnostic tool.
So the eGFR has become a useful diagnostic tool. The important thing is to be aware of its limitations, and not to obsess about its numbers.

Adiponectin- Unlikely hero in the body

Adiponectin- Hormone responsible for putting out small fires.

The body is constantly under attack from the abuse of living. Internally there are all these injuries occurring at the molecular level, causing damage that spreads like wildfire until it is out of control. Metabolic syndrome is an example of this. What is it? This is a term used to describe a group of conditions that put patients at higher risk of developing type two diabetes and/or heart disease. Patients having three or more of the following are considered to have Metabolic Syndrome:
- High fasting glucose (greater than 5.6 mmol/L)
- High Blood Pressure (130/85 of higher)
- High Triglyceride (> 1.7 mmol/L)
- Decreased HDL (<1.0 in men, <1.3 in women) (A trick to remember which cholesterol is which is that HDL is the Healthy one, LDL is the Lousy one )
- Abdominal obesity or too much fat around the waist (>102 cm (40 inches) for men, >88 cm (35 inches) for women)

There is some debate on what causes Metabolic Syndrome. Is it due to increased insulin resistance, genetics, old age or life style? Wouldn’t it be nice if there was a diligent fulltime fighter in the human body that went around putting out the little brush fires these conditions caused before they became five alarm threats to our health?
Researchers have discovered a hormone that does this and it is from an unlikely source.
After studying the cells found in adipose (fatty) tissue called adipocytes, it was discovered that forty percent of the expressed genes were unknown or novel genes, even the gene that was most abundant and specific for an adipocyte. Further research identified a protein produced by adipocytes termed adiponectin.
Logic would determine that the more adipose tissue you have the more adipocytes present would result in increased levels of adiponectin, correct?
Wrong. To everyone’s surprise the higher the body mass index (BMI) the lower the adiponectin levels. Healthy patients with low levels of body fat had higher levels of adiponectin. Patients with Metabolic Syndrome and diabetes also had low levels of adiponectin.
So what does adiponectin exactly do?
It can help prevent atherosclerosis in blood vessels. Atherosclerosis is damage to cell walls caused by accumulation of fatty materials, such as LDL cholesterol and white blood cells called monocytes. Adiponectin has been found to prevent this kind of cell wall damage by having inhibitory affect against molecules that cause LDL and monocytes from sticking to vessel walls. This protein once secreted by adipocytes enters into the blood stream and looking for damaged cells lining vessel walls to repair, putting out small fires before they burn out of control.
The bad news is that measurement of adiponectin is not routinely done in the medical lab... yet. But when it does, it will help determine which patients will be at risk of developing Metabolic Syndrome. A good article to read about this can be found at :
http://atvb.ahajournals.org/cgi/reprint/24/1/29
Thank you for taking the time to read my posting. I look forward to your thoughts and comments.
Regards,

Mark Hawkins