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Diagnosis of acute poststreptococcal glomerulonephritis
Last reviewed: 23.04.2024
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Acute poststreptococcal glomerulonephritis is always manifested by pathological changes in the urine. Be sure to have hematuria and proteinuria, usually there are cylinders. In freshly collected urine samples, erythrocyte cylinders are often found, and with the aid of phase contrast microscopy it is possible to identify dysmorphic ("altered") erythrocytes, indicating the glomerular origin of hematuria. Also, the diagnosis of acute poststreptococcal glomerulonephritis detects epithelial cells of the tubules, granular and pigmented cylinders, and leukocytes. In patients with severe exudative glomerulonephritis, leukocyte cylinders are sometimes found. Proteinuria is a characteristic sign of acute poststreptococcal glomerulonephritis; nephrotic syndrome at the onset of the disease is present in only 5% of patients. Sometimes transient growth of proteinuria is noted in 1-2 weeks of the disease as the recovery rate of CF.
[Laboratory diagnostics of acute poststreptococcal glomerulonephritis
Urine: protein, red blood cells, cylinders. Glomerular filtration: at the beginning it is lower in some patients. (T serum creatinine> 2 mg% in 25% of cases). Antistreptococcal antibodies:
- in patients with pharyngitis> 95%;
- in patients with skin infection - 80%;
- false positive results - 5%;
- early antibiotic therapy suppresses the antibody response. CH50 and / or C3, C4: decrease in levels> 90%. Hypergammaglobulinemia is 90%. Polyclonal cryoglobulinemia is 75%.
The serum creatinine concentration is usually elevated (approximately 25% of patients - more than 2 mg / dl), although some remain within the upper limit of the norm. The rate of CF is initially almost always reduced, but as the resolution of the disease returns to normal values.
In the first 2 weeks of jade activity, the C3 and CH50 levels are reduced more than in 90% of patients, C4 usually remains normal or sometimes slightly reduced; its expressed decrease indicates the presence of another disease (mesangiocapillary glomerulonephritis, lupus nephritis, essential mixed cryoglobulinemia). The level of the properdin is usually low and reflects the interest of the alternative pathway of complement activation. In most cases, the complement indicators return to normal by week 4, but sometimes it lasts up to 3 months. C3-nephritic factor is absent or is detected in low concentration, high and persistent increase in its concentration is more typical for mesangiocapillary glomerulonephritis.
90% of patients have hypergammaglobulinemia, 75% have polyclonal transient cryoglobulinemia.
Antibodies to the extracellular products of streptococcus: anti-streptolysin-O, anti-hyaluronidase, antistreptokinase, antinicotinamide adenine dinucleotidase (anti-NAD) and anti-DNase B are detected in more than 95% of patients with pharyngitis and in 80% of patients with skin infection. Antistreptolysin-O, anti-DNase B, anti-NAD and anti-hyaluronidase titres usually increase after pharyngitis, while anti-DNase B and anti-HA are more common after skin infection. These tests for streptococcal infection are quite specific: false positive results are no more than 5%. Since the prevalence of streptococcal infection among children is quite high, elevated titers indicate primarily the presence of streptococcal infection in patients , and not the presence of nephritis. The titers of these antibodies rise 1 week after the onset of infection, reach a peak after 1 month, and gradually return within a few months to their baseline level, which was before the disease. Antibodies against M-proteins are type-specific and indicate immunity to certain strains. They are detected 4 weeks after the onset of infection and persist for several years. Early treatment of acute poststreptococcal glomerulonephritis with antibiotics often breaks off the development of the antibody response to both extracellular products and to M streptococcal proteins. Therefore, negative results of the study on anti-streptococcal antibodies in patients who previously received antibiotics do not exclude the diagnosis of a streptococcal infection.