Patients often come to the clinic with positive “anti-O” (anti-streptococcal hemolysin O, ASO) results, and they are usually worried because they are often torn between streptococcal infection and non-infection, arthritis and non-arthritis, treatment and no treatment, how to treat, and how long to treat, They are often at a loss as to what to do and how long to treat, because different doctors say different things. It is also common to see asymptomatic but purely ASO-positive patients receiving long-acting penicillin therapy for a long time, and it seems that the appropriateness of such treatment is not clear in a few words. So, today we will talk about those things that are “anti-O” positive, and try to make sense of it for you. The relationship between rheumatic fever and group A hemolytic streptococci Acute rheumatic fever is a systemic inflammatory disease closely related to group A hemolytic streptococcal (GAS) infection pharyngitis, which is a delayed, non-suppurative disease after GAS infection and can cause multi-organ organ involvement, including multi-joint involvement, cardiitis and valvulitis, central nervous system lesions, skin lesions, etc. What is the relationship between rheumatic fever and “rheumatoid arthritis”? Rheumatic fever may not be well known to the general public, but the name “rheumatoid arthritis” is familiar to the general public. However, the term “rheumatoid arthritis” itself is controversial in the academic community and is not a widely accepted diagnostic name. “This can lead to misunderstanding and even bias in diagnosis and treatment. In fact, when people say “rheumatoid arthritis”, they generally refer to the joint lesions of rheumatic fever, and another condition is reactive arthritis after streptococcal infection (wandering arthritis after streptococcal infection without heart inflammation). Does a positive ASO mean rheumatic fever? Streptococcal hemolysin O is one of the metabolites of Streptococcus haemolyticus, which is antigenic, and the full name of ASO is anti-streptococcal hemolysin O. As the name suggests, it is an antibody produced in the body 2-3 weeks after the human body is infected by Streptococcus haemolyticus, and it is generally considered that an ASO of more than 240 units in adults or more than 320 units in children is over the limit, indicating that the body currently exists or has had Streptococcus haemolyticus infection. ASO is currently the most widely used clinical method to detect GAS infection. Elevated ASO can be found in 80% of patients with rheumatic fever, so when ASO is positive, it should be taken seriously. However, in practice, the specificity of the ASO test is not very high, and a positive ASO can be present in infections of other streptococcal groups (group G, group C) or even in infections of other species of bacteria that can produce ASO analogues. Therefore, a positive ASO is not the same as a group A hemolytic streptococcal infection, let alone a presenting group A hemolytic streptococcal infection, and it is even less likely to be equated with rheumatic fever. Does a positive ASO need treatment? Returning to the confusion mentioned at the beginning of this article, do asymptomatic patients with pure ASO positivity need treatment? Our answer is that treatment is not needed for those who are purely ASO positive, have no clinical symptoms and no history of rheumatic fever, and no GAS pharyngitis or tonsillitis. Only the following two conditions require prophylactic medication: 1. Primary prevention: those without a history of rheumatic fever but with GAS pharyngitis tonsillitis. Returning again to the question at the top of the article, it is clearly inappropriate for asymptomatic but purely ASO-positive individuals to receive long-term treatment with long-acting penicillin. The inappropriateness is, but not limited to, the following two points: first, such patients are not indicated for treatment; second, even for primary prevention, the treatment regimen is not long-term treatment with long-acting penicillin. The primary prophylaxis regimen for rheumatic fever is not new, as we have been told since the 1950s that we should treat with benzathine penicillin G injections for 9-11 days (long-term treatment is not required). Current research suggests that for primary prevention, only a single dose of intramuscular benzylpenicillin G should be used, specifically 600,000 units intramuscularly for children under 27 kg and 1,200,000 units intramuscularly for children or adults over 27 kg. Or amoxicillin/penicillin V oral 250mg x 2-3 times/day (for children under 27kg) and 500mg x 2-3 times/day (for children or adults over 27kg) for 10 days. 2.Secondary prevention: Patients who have suffered from rheumatic fever. Secondary prevention is for patients who have suffered from rheumatic fever, which has a high risk of recurrence and involvement of cardiac lesions, so the course of preventive treatment should be longer. Options include intramuscular benzathine penicillin G every 4 weeks, oral penicillin V/amoxicillin twice daily, and oral sulfadiazine once daily; specific dosing options and dosages are not covered in depth here. The course of secondary prevention should depend on the severity of the previous rheumatic fever condition. For rheumatic fever combined with mild heart involvement, secondary prevention should be given for 10 years or until the age of 25 years; for rheumatic fever combined with severe heart inflammation or valve surgery, secondary prevention should be given for life; for rheumatic fever without heart involvement, if long-term exposure to children (e.g., mothers, babysitters, kindergarten teachers, etc.) is needed, secondary prevention should not be discontinued until the exposure factors are eliminated. At this point, when we look back at the case of the asymptomatic but purely ASO-positive person who received long-acting penicillin for a long period of time, we are actually mistaking this group of people for patients with a previous history of rheumatic fever with cardiac involvement for secondary treatment. So far, we have finished introducing GAS, ASO, rheumatic fever and prophylaxis. We provide rheumatology and immunology services and recommend online consultation or face-to-face consultation for individualized treatment based on evidence-based medicine if corresponding symptoms exist. Warm tips: 1. Rheumatic fever is associated with GAS infectious pharyngitis, which can cause multi-organ organ involvement. 2.”Rheumatoid arthritis” is not a widely recognized diagnostic name, but generally refers to the arthritic lesions of rheumatic fever and reactive arthritis after streptococcal infection. 3.ASO positive ≠ group A hemolytic streptococcal infection ≠ current group A hemolytic streptococcal infection ≠ rheumatic fever. 4. Those who are purely ASO positive with no clinical symptoms and no history of rheumatic fever and no GAS pharyngitis tonsillitis do not need treatment. 5.People who have no history of rheumatic fever but have GAS pharyngitis and tonsillitis need primary prevention, but primary prevention is not long-term use of long-acting penicillin. 6, patients who have had rheumatic fever need secondary prevention, and the course of secondary prevention is determined by the severity of previous rheumatic fever. 7.Patients with acute rheumatic fever with current symptoms should consult a rheumatologist.