Antistreptokinase antibodies and the response to thrombolysis with streptokinase in patients with acute ST elevation myocardial infarction

Background and objective A large number of patients with ST elevation myocardial infarction (STEMI) continue to receive streptokinase (SK) in the developing countries. High levels of antistreptokinase (ASK) antibodies can result in failure of thrombolysis. This study was conducted to assess the presence of ASK antibodies in the general population and its effect on the outcome of thrombolysis with SK. Design Prospective observational study. Setting A tertiary care medical institute in Vellore, India. Patients 148 patients presenting with STEMI undergoing thrombolysis with SK were recruited. Main outcome measures The response to SK was assessed by reperfusion markers in the patients and they were categorised as good responders, probable responders and non-responders. Those who responded to SK and probable responders were considered to have benefited from thrombolysis. Results 60 patients (40%) had ASK antibody titres higher than the median. In patients with a window period <6 h, 73% of patients who benefited from thrombolysis had low ASK titres while 100% of the patients who did not benefit had high ASK titres (p=0.001). Similarly, in patients with a window period >6 h, 89% of patients who benefited from thrombolysis had low ASTK titres while 54% of those who did not benefit had high ASK titres (p=0.002). Conclusions ASK antibodies are present in significant titres in a large proportion of patients in developing countries, which leads to failure of thrombolysis in such patients. In endemic areas with high endemic streptococcal infection, alternative agents should be used for thrombolysis in STEMI.