SLO

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Streptolysin is an exotoxin produced by group A streptococci, referred to as anti-"O" or ASO. It can dissolve red blood cells and is toxic to many kinds of cells in the body. After the human body is infected with hemolytic streptococcus, a large amount of anti-streptococcal hemolysin O (anti-"O") antibodies can appear in the serum.

Detection of anti-"O" can be used as an auxiliary diagnosis of allergic diseases (rheumatic fever, glomerulonephritis) after streptococcal infection.

Reference value

Normal reference value: adults <500U, children <250U. The normal value varies with age, season, climate, streptococcal prevalence, and especially by region. In rheumatoid patients, ASO rises above 400 units.

Classifications

Fichy et al. divided rheumatoid ASO into four serum types:

1. Anti-streptococcal hemolysin type: when ASO is elevated and RF is negative, it is seen in rheumatism,
2. Agglutinative type: when ASO is normal and RF is positive, it indicates a poor prognosis;
3. Mixed type: elevated ASO, positive RF, seen in rheumatoid;
4. Normal type: ASO is negative, RF is negative, rheumatoid can be ruled out.

Mechanism

A metabolite produced by Streptococcus sanguis can lyse red blood cells, so this product is named "O" hemolysin. After the human body is infected with group A hemolytic streptococcus, "O" hemolysin exists in the body as an antigenic substance. In order to counteract the determination of the antibody content that can neutralize streptolysin "O", it is called the anti-streptolysin "O" test. The value of resistance to "O" is calculated in units, and there are 100, 125, 166, 250, 333, 500, 625, 833, 1250, 2500 and other levels. Normal kernels are generally below 500 units. If it is higher than 500 units, it means that there has been a recent hemolytic streptococcal infection. Some patients have elevated resistance to "O" but have no symptoms such as joint soreness. They cannot be considered as suffering from rheumatoid arthritis. It can only mean that they have had a recent hemolytic streptococcal infection, such as tonsillitis, pharyngitis, scarlet fever, etc. However, the cause of rheumatoid arthritis is indeed related to the infection of streptococcus. Therefore, in the active period of rheumatoid arthritis, the resistance "O" will increase.

Research

According to research, Coxsackie B virus, hypercholesterolemia, hemolysis, hepatitis, nephrotic syndrome and other diseases can show non-specific anti-"O" increase, but the titer is not very high, as is rheumatoid arthritis. It is generally believed that the onset of rheumatoid arthritis may be related to the infection of certain microorganisms, which cause abnormal immune responses after infection. Streptococcus may also be mixed in it, and part of it is involved in the infection, so anti-"O" appears. In addition, patients with rheumatoid arthritis have "long sickness and weakness", have poor resistance, and are prone to be invaded by streptococci. It is common in clinical practice that patients with rheumatoid arthritis have pharyngitis. There are also some patients with arthritis who are treated with adrenal cortex hormones or immunosuppressive agents, and their anti-infection ability is significantly reduced, which is also the cause of combined streptococcal infection. Anti-“O” is not like erythrocyte sedimentation rate and C-reactive protein as an index to judge the severity of the disease and measure the treatment effect. Therefore, it is not a routine item in the examination of rheumatoid arthritis.