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Reference ranges (reference intervals) for blood tests are sets of values used by a health professional to interpret a set of medical test results from blood samples. Reference ranges for blood tests are studied within the field of clinical chemistry (also known as "clinical biochemistry", "chemical pathology" or "pure blood chemistry"), the ...
Hyponatremia or hyponatraemia is a low concentration of sodium in the blood. [4] It is generally defined as a sodium concentration of less than 135 mmol/L (135 mEq/L), with severe hyponatremia being below 120 mEq/L. [3] [8] Symptoms can be absent, mild or severe.
Serum creatinine (a blood measurement) is an important indicator of kidney function, because it is an easily measured byproduct of muscle metabolism that is excreted unchanged by the kidneys. Creatinine itself is produced via a biological system involving creatine , phosphocreatine (also known as creatine phosphate), and adenosine triphosphate ...
The normal range of GFR, adjusted for body surface area, is 100–130 average 125 (mL/min)/(1.73 m 2) in men and 90–120 (mL/min)/(1.73 m 2) in women younger than the age of 40. In children, GFR measured by inulin clearance is 110 (mL/min)/(1.73 m 2 ) until 2 years of age in both sexes, and then it progressively decreases.
The age term is (140 – age). This means that a 20-year-old person (140 – 20 = 120) will have twice the creatinine clearance as an 80-year-old (140 – 80 = 60) for the same level of serum creatinine. The C-G equation assumes that a woman will have a 15% lower creatinine clearance than a man at the same level of serum creatinine.
Measurements of urea and creatinine (Cr) in the blood are used to assess renal function. For historical reasons, the lab test measuring urea is known as "blood urea nitrogen" (BUN) in the US. The BUN:Cr ratio is a useful measure in determining the type of azotemia and will be discussed in each section below. A normal BUN:Cr is equal to 15. [3]
The fractional excretion of sodium (FE Na) is the percentage of the sodium filtered by the kidney which is excreted in the urine. It is measured in terms of plasma and urine sodium , rather than by the interpretation of urinary sodium concentration alone, as urinary sodium concentrations can vary with water reabsorption .
Severe symptoms are usually due to acute elevation of the plasma sodium concentration to above 157 mmol/L [10] (normal blood levels are generally about 135–145 mmol/L for adults and elderly). [10] Values above 180 mmol/L are associated with a high mortality rate, particularly in adults. [ 11 ]