A few minutes ago, I posted a Wiki article about Creatinine. GFR blood tests are the standard in determining lower kidney function in most developed countries. A higher creatinine, or waste in the blood, will usually indicate a decreased kidney function. Put simply, the liver, the kidneys and the skin are excretory organs that allow waste products to be flushed from the body. GFR testing is delivered by serum blood test and urine tests, to determine whether a person’s creatiinine levels are high or low.
The problem is described in this excerpt from the last article that I just posted minutes ago:
A rise in blood creatinine level is a late marker, observed only with marked damage to functioning nephrons. Therefore, this test is unsuitable for detecting early-stage kidney disease. A better estimation of kidney function is given by calculating the estimated glomerular filtration rate (eGFR). eGFR can be accurately calculated using serum creatinine concentration and some or all of the following variables: sex, age, weight, and race, as suggested by the American Diabetes Association without a 24-hour urine collection. Many laboratories will automatically calculate eGFR when a creatinine test is requested. Extensive discussion of eGFR algorithms can be found in the Renal function article.
A concern as of late 2010 relates to the adoption of a new analytical methodology, and a possible impact this may have in clinical medicine. Most clinical laboratories now align their creatinine measurements against a new standardized isotope dilution mass spectrometry (IDMS) method to measure serum creatinine. IDMS appears to give lower values than older methods when the serum creatinine values are relatively low, for example 0.7 mg/dL. The IDMS method would result in a comparative overestimation of the corresponding calculated GFR in some patients with normal renal function. A few medicines are dosed even in normal renal function on that derived GFR. The dose, unless further modified, could now be higher than desired, potentially causing increased drug-related toxicity. To counter the effect of changing to IDMS, new FDA guidelines have suggested limiting doses to specified maxima with carboplatin, a chemotherapy drug.
The problem exists when most laboratories are using the IDMS method to determine serum creatinine levels. As described in this excerpt above, this method often results in higher creatinine readings in people with mild kidney dysfunction. The resulting therapies and medications can then be prescribed by doctors, resulting in over estimating the amount of dosage for these patients, resulting in the possibility of too high a dose of medicines being prescribed, which could result in further damaging peoples kidneys.
If you are suffering from a mild form of renal dysfunction, please take this warning seriously. Your doctor could be overdosing you with the medications that are prescribed to ameliorate your condition. One example of this is the case where someone with renal dysfunction is also suffering from depression, due to their illness. In some cases a dangerous anti-depressant called Lithium Carbonate is prescribed for the depression. If as I have described above, the IDMS testing overestimates the degree of renal dysfunction in that patient, they could be prescribed a higher dosage of Lithium Carbonate, to counter their depression. This could result in serious renal toxicity and could damage their kidneys even further.
Lithium Carbonate taken in higher dosages is not easily filtered by the blood. It consists of Lithium salt, which can be difficult to filter as the salt tends to accumulate in the bloodstream, resulting in further renal damage.