Analysis of Antistreptolysin Titre in Serum Samples

Introduction:
Antistreptolysin O (ASO) is an antibody produced in response to an infection caused by Group A streptococci (GAS). It is commonly used as a diagnostic tool to determine the presence and severity of recent or ongoing GAS infections. ASO levels in the serum can provide valuable information about a patient’s immune response and help clinicians make more accurate diagnoses and treatment decisions. In this article, we will discuss the analysis of Antistreptolysin Titre in serum samples and its clinical significance.

ASO Test Procedure:
The ASO test is a simple and commonly performed laboratory assay that measures the level of ASO antibodies in a patient’s serum. The test is often performed using a nephelometry or latex agglutination method. In the nephelometry method, ASO reacts with specific antibodies, and the degree of light scattering is measured and directly proportional to the ASO concentration. In the latex agglutination method, ASO reacts with latex beads coated with streptolysin O, leading to the formation of visible clumps.

Clinical Significance:
Elevated ASO titers indicate a recent or ongoing infection caused by GAS. The diagnosis of acute rheumatic fever (ARF), post-streptococcal glomerulonephritis (PSGN), and other streptococcal infections heavily relies on the ASO titer. However, it is important to note that a high titer does not necessarily confirm a current infection, as ASO levels can remain elevated for several weeks after the infection has resolved.

Interpretation of Results:
ASO titers are typically reported in Todd units or IU/mL. The interpretation of results depends on the reference range established by each laboratory. Generally, a low or negative ASO titer indicates the absence of recent or ongoing GAS infection. A rising titer over time, however, suggests an active infection. Clinicians rely on comparing consecutive ASO titers to monitor the course of the disease and evaluate the effectiveness of treatment.

Limitations and Considerations:
It is crucial to consider that ASO titers are not pathognomonic of GAS infections. Other bacteria, such as Group C or Group G streptococci, can also cause false-positive results. Additionally, some individuals may not produce significant ASO levels despite having a GAS infection, leading to false-negative results. Therefore, ASO titers should always be interpreted in conjunction with the patient’s clinical presentation, medical history, and other laboratory findings.

Conclusion:
The analysis of Antistreptolysin Titre in serum samples is an essential tool for diagnosing and monitoring GAS infections, particularly in cases of acute rheumatic fever and post-streptococcal glomerulonephritis. ASO titers help clinicians determine the presence, severity, and progression of the infection, facilitating appropriate treatment decisions. However, it is important to interpret ASO results cautiously, considering both the limitations of the test and other clinical factors. A multidisciplinary approach involving clinical evaluation, patient history, and additional laboratory investigations is crucial for accurate diagnosis and patient management.