Uric acid in blood serum

Uric acid is a product of the exchange of purine bases, which are part of complex proteins - nucleoproteins. Formed uric acid is secreted by the kidneys. Uric acid in the extracellular fluid, including blood plasma, is present in the form of a sodium salt( urate) at a concentration close to saturation, so it is possible to crystallize it when the maximum normal values ​​are exceeded. Reference values ​​of the concentration of uric acid in the blood serum are presented in Table.

In adult men, the upper limit of the normal concentration of uric acid in the blood serum is 0.42 mmol / l. In an aqueous solution with a pH of 7.4, at a temperature of 37 ° C and an ionic strength equal to that of

Fig. Nomogram for rapid determination of GFR

Fig. Nomogram for the rapid determination of GFR

in plasma, the solubility of sodium urate is 0.57 mmol / l;in plasma in the presence of proteins is somewhat lower. Knowledge of these constants is of great practical importance, so it allows to determine the goals of treatment for patients with gout, that is, to what level it is necessary to reduce the concentration of uric acid in the blood serum in order to achieve dissolution of urates in the extracellular fluid and tissues.

Table Reference values ​​for serum uric acid concentration

Reference values ​​for uric acid concentration in blood serum

Increase in uric acid concentration in the blood( hyperuricemia) is of great importance for the diagnosis of gout. There are primary gout, in which the accumulation of of uric acid in the blood of is not caused by any other disease, and secondary, which develops due to disruption of kidney function, increased purine formation in hematological diseases accompanied by the decay of a variety of nuclear cells, after irradiation with X-rays,malignant neoplasms, cardiac decompensation, destruction of tissues during fasting and other cases. Thus, primary and secondary gout occur as a result of impaired excretion of uric acid or its excess production.

Primary gout is a consequence of hyperuricemia developing with delayed excretion( 90% of cases) or in excess synthesis( 10% of cases) of uric acid. Crystals of urate can be deposited in joints, subcutaneous fat( tofus) and kidneys. The risk of developing gout depending on the concentration of uric acid in the blood serum is given in Table 1.

Table Risk of gout development depending on serum uric acid concentration

Table Risk of gout depending on serum uric acid concentration

Determination of blood concentrationuric acid is particularly important in the diagnosis of asymptomatic hyperuricemia( urinary

acid in the blood in men above 0.48 mmol / l, in women above 0.38 mmol / l) and the latent development of the goutnical kidney( 5% of men).Acute gouty arthritis occurs in 5-10% of patients with asymptomatic hyperuricemia. Hyperuricemia in patients with gout is unstable, can be undulating. Periodically, the content of uric acid may decrease to normal levels, but often an increase of 3-4 times compared with the norm. To obtain accurate data on the content of uric acid in the blood, most adequately reflecting the level of its endogenous formation, it is necessary to appoint malopurinovuyu diet for 3 days before the study. In addition, it is necessary to know that during an acute attack of gout in 39-42% of patients the concentration of uric acid in the blood serum is reduced to normal values.

Criteria for diagnosing gout:

■ serum uric acid concentration in men is above 0.48 mmol / l, in women above 0.38 mmol / l;

■ presence of gouty nodules( tophi);

■ detection of urate crystals in synovial fluid or tissues;

■ history of acute arthritis, accompanied by severe pain, which started suddenly and died down within 1-2 days.

The diagnosis of gout is considered reliable if at least two of any signs are detected.

Secondary gout can develop with leukemia, vitamin B12 deficit anemia, polycythemia, sometimes with some acute infections( pneumonia, erysipelas, scarlet fever, tuberculosis), liver and biliary tract diseases, diabetes mellitus with acidosis, chronic eczema, psoriasis,urticaria, kidney disease, acidosis, acute alcohol intoxication( secondary "gout alcoholic").

Diagnostic value of determining the content of uric acid in the blood with kidney failure is minimal.