What tests do gout patients need to do?

Laboratory examination is of great significance to the diagnosis of gout, especially the discovery of urate, which is the basis of diagnosis.

First, blood and urine routine and erythrocyte sedimentation rate

1. During acute attack, the number of white blood cells in peripheral blood increased, usually (10 ~ 20) × 109/L, and rarely exceeded 20 × 109/L .. The neutrophils increased accordingly. People with decreased renal function may have mild or moderate anemia. The erythrocyte sedimentation rate increases rapidly, usually less than 60 mm/h.

2. Routine urine examination generally does not change in the early stage of the disease. Those who involve the kidney may have proteinuria, hematuria and pyuria, and occasionally tubular urine; Kidney calculi's patients can see obvious hematuria and acid urolithiasis.

Second, the determination of serum uric acid

The content of serum uric acid in most patients increased during acute attack. It is generally considered that the uricase method is 4 16μmol/L(7mg/dl) for males, and >: 357μmol/L(6mg/dl), which has diagnostic value. If uric acid excretion drugs or adrenocortical hormones have been used, the serum uric acid content may not be high. The remission period can be normal. 2% ~ 3% patients have typical gout attacks, and the serum uric acid content is lower than the above level. There are three explanations: ① there is a big difference between the central body temperature and the peripheral joint temperature gradient; ② Under stress, the body secretes more adrenocortical hormones, which promotes the excretion of blood uric acid, while the content of sodium urate in the distal joint is still high; ③ The role of uric acid excretion drugs or corticosteroids.

Third, determination of uric acid content

In the absence of purine diet and drugs affecting uric acid excretion, the total uric acid of normal male adults in 24 hours does not exceed 3.54mmol/(600mg/24h). The uric acid excretion of 90% patients with primary gout is less than 3.54mmol/24h. Therefore, urine uric acid excretion is normal, and gout cannot be ruled out, while urine uric acid is more than 750mg/24h, suggesting that uric acid is produced too much, especially in non-renal secondary gout, blood uric acid is increased, and urine uric acid is also significantly increased.

Four, joint cavity puncture examination

At the onset of acute gouty arthritis, there may be effusion in the swollen joint cavity. It is of great diagnostic significance to draw synovial fluid with an injection needle for examination. Even in asymptomatic period, sodium urate crystals can be found in many joints. Uric acid salt crystals can be found in synovial fluid of about 95% acute gouty arthritis.

(1) polarized light microscopy

When synovial fluid is placed on the glass slide, the slow vibration image of birefringent fine needle-like sodium urate crystal can be seen inside or outside the cell. The first-stage red compensation prism is adopted, and the urate crystal direction is yellow when it is parallel to the mirror axis and blue when it is vertical.

(2) General microscopic examination

Sodium urate crystal is rod-like and needle-like, and the detection rate is only half of that of polarizing microscope. If heparin is added to synovial fluid, it can be centrifugally precipitated, and the detection rate can be improved by objective lens inspection.

(3) Determination by ultraviolet spectrophotometer

Qualitative analysis of synovial fluid or contents of suspected gout nodules by ultraviolet spectrophotometer is the most valuable method to determine sodium urate. The method is to determine the absorption spectrum of the sample to be tested first, and then compare it with the known absorption spectrum of sodium urate. If they are the same, the tested substance is a known compound.

(4) murexide test

This test can be used for further confirmation of samples found to contain sodium urate by ordinary optical microscope or polarized microscope. This method is simple and easy. Its principle is that sodium urate is heated with nitric acid to generate urea, and then ammonia water is added to generate purplish red ammonium urate.

(5) urate dissolution test

In the synovial fluid with urate crystals, after adding uricase to keep warm, urate crystals degrade into allantoin and disappear.

Five, gout nodule content inspection

For gout nodules, the positive rate of specific urate is extremely high by absorbing its contents through biopsy or puncture, or taking chalk sticky substance smear from skin ulcer.

Six, X-ray examination

Uric acid salt is easy to deposit in and near facet joints, causing chronic inflammatory reaction and destroying cartilage and bone cortex. Photos of these parts show that there are shadows of light transmission defects on the articular surface or the cortical bone, such as perforation, moth-eaten, honeycomb or cyst. Bone mineral density around the lesion is normal or hyperplasia, and the boundary is clear, which is beneficial to distinguish it from other joint lesions. Among the 160 cases reported by Meng et al., 76 cases (60.3%) showed the above-mentioned typical changes of bone cortex, of which 4 cases caused fractures.