Antistreptolysin O (Antistreptolysin-O, ASLO)

Antistreptolysin O (ASLO) is an antibody directed against the enzyme streptolysin O, which is produced by the bacterium group A beta-hemolytic streptococcus (Streptococcus pyogenes). This microorganism can cause a variety of diseases, from mild infections to severe systemic complications. Testing for ASLO levels in the blood can detect previous or current streptococcal infection.

Role of ASLO: ASLO occurs as a response of the immune system to exposure to streptococcal antigens. Streptolysin O is a toxin secreted by streptococci that causes the destruction of red blood cells and the lysis of biological membranes. In response, the body produces antibodies called ASLO. They can remain in the body for a long time after infection.

ASLO level measurement: ASLO level is determined by immunological methods, in particular enzyme-linked immunosorbent assay (ELISA). A blood sample is taken from a vein. An elevated ASLO level indicates contact with streptococci, but does not indicate a specific disease state. After infection, ASLO level may increase after 1-3 weeks and remain elevated for some time, making it an indicator of a previous infection.

Clinical significance:

1. Rheumatic fever: Elevated ASLO levels may be associated with rheumatic fever, a systemic infectious-allergic disease that can affect heart valves, joints, and other organs. A peculiar immune response to a streptococcal infection can cause an attack on one's own tissues.
2. Post-influenza complications: In some cases, streptococcal infection can follow influenza or other infectious diseases, leading to complications. Monitoring ASLO levels can help detect such complications.
3. Acute glomerulonephritis: This is a kidney disease that can develop after a streptococcal infection. Elevated ASLO levels can be one indicator of this condition.
4. Other complications: Elevated ASLO levels may accompany other complications such as vasculitis, inflammatory reactions, etc.

Conclusion: Antistreptolysin O (ASTO) is an important immunological test that helps to establish the presence of beta-hemolytic streptococci. Elevated ASLO levels may indicate previous infection and raise suspicion for various complications, including rheumatic fever and kidney damage. However, it is important to note that ASLO levels alone are not specific for a particular disease, and the diagnosis should be made in conjunction with other clinical findings and examinations.