Anti-streptolysin O Titers in Patients with Poststreptococcal Complications: A Retrospective Observational Study

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Introduction: Anti-streptolysin O (ASO) antibodies serve as an important marker of recent Group A Streptococcus (GAS) infection and are crucial in diagnosing immune-mediated post streptococcal complications, such as Acute Rheumatic Fever (ARF) and Post Streptococcal Glomerulonephritis (PSGN). Aim: To evaluate ASO titers in patients with suspected poststreptococcal immune-mediated complications. Materials and Methods: A retrospective observational study was conducted in the Department of Microbiology, Dhiraj Hospital, Smt. B.K. Shah Medical Institute and Research Centre, Sumandeep Vidyapeeth Deemed to be University, Vadodara, Gujarat, India, over a period of two years from January 2023 to December 2024. A total of 67 serum samples with ASO titers ≥200 IU/mL were included. Patients presenting with clinical features suggestive of post streptococcal sequelae such as fever, joint pain, haematuria, facial puffiness, or a recent history of sore throat (within 2–3 weeks) were included in the study. Demographic data, clinical presentation, ASO titers, and provisional diagnoses were recorded and analysed. Data were expressed as frequency and percentage {n (%)}. Results: The majority of ASO-positive cases were children aged 6–15 years, 38/67 (56.7%), with a male predominance 41/67 (61.2%). The most common clinical features included joint pain 33/67 (49.2%), fever 25/67 (37.3%), and haematuria or facial puffiness 17/67 (25.4%). The highest recorded ASO titer was 1100 IU/mL. The most common provisional diagnoses were PSGN 21/67 (31.3%) and suspected acute rheumatic fever 19/67 (28.3%). Conclusion: Quantitative ASO measurement using MISPA i3 nephelometry provides reliable and rapid detection of recent streptococcal infections. These findings reinforce its value in diagnosing post-streptococcal immune-mediated complications, particularly among paediatric populations, supporting timely clinical intervention and management.