Glomerular filtration rate, or simply DFG, is a laboratory measure that allows the family doctor and nephrologist to evaluate the functioning of a person’s kidneys, which is an important measure for the diagnosis and verification of the stage of chronic renal failure (CKD), making TFG also critical to establishing the best treatment , if necessary.
To calculate the glomerular filtration rate it is necessary to take into account the sex, weight and age of the person, since it is normal for DFG to decrease as the person ages, which does not necessarily indicate kidney injuries or alterations.
- Several calculations are proposed to determine the glomerular filtration rate.
- However the most commonly used in clinical practice are those that take into account the amount of creatininine in the blood or the amount of cystatin C.
- Which is the most studied today.
- Since the amount of creatinine may be interference with other factors.
- Including the diet.
- So it does not become an appropriate marker for the diagnosis and monitoring of CKD.
The glomerular filtration rate is determined in the laboratory by calculations that must mainly take into account the age and sex of the person, since these factors interfere with the result; however, to calculate DFG, a blood sample must be taken for measurement. creatinine or cystatin C, as recommended by your doctor.
Glomerular filtration can be calculated taking into account both creatinine concentration and cystatin C concentration, although creatinine is the most commonly used, is not the most appropriate, as its concentration may be subject to interference from other factors, such as diet, physical activity, inflammatory diseases and the amount of muscle mass and therefore does not necessarily represent renal function.
On the other hand, cystatin C is produced by nucleated cells and regularly filtered into the kidneys, so the concentration of this substance in the blood is directly related to DFG, thus being a better marker of renal function.
The purpose of glomerular filtration flow is to check the functioning of the kidneys, since it takes into account the dosage of substances that are filtered to the kidneys and are not reabsorbed in the blood, being essentially eliminated in the urine. for example, this protein is filtered through the kidneys and a small amount is reabsorbed into the bloodstream, so under normal conditions creatinine concentrations in the urine much higher than those in the blood can be verified.
However, in case of renal modification, the filtration process can be modified, so that less creatinine is filtered through the kidneys, resulting in a higher concentration of creatinine in the blood and a decrease in glomerular filtration rate.
The glomerular filtration rate may vary depending on the sex and age of the person, the DFG values when calculated with creatinine are:
Depending on age, normal DFG values are generally
Values may vary from lab to lab, however when DFG is below the normal baseline for age, the possibility of kidney disease is considered, being recommended by additional tests to complete the diagnosis, such as imaging and biopsy tests. In addition, depending on the values obtained for DFG, the doctor can check the stage of the disease and thus indicate the most appropriate treatment.