<![CDATA[Background: In the era of personalized medicine, biomarkers have become an important tool for detecting and predicting asthma episodes over the last decade. Urinary bromotyrosine has several advantages as a potential biomarker for asthma, including its stability and the practicality of non-invasive urine sample collection. Methods: This is an analytical observational study with a cross-sectional design. From May to December 2023, the study involved 82 patients aged 6 to 65 years from the Harum Melati Clinic in Pringsewu. The participants underwent spirometry, differential leukocyte count, urinalysis, and chest X-rays. The severity of asthma obstruction was classified as mild (n = 66) or moderate-severe (n = 6), with non-asthmatic patients (n = 10) served as the control group. Urinary bromotyrosine levels were tested using the 3-BrY ELISA Kit EU3112. Results: Urinary bromotyrosine levels were significantly higher in asthma patients compared to the control group (154.11 ng/mL vs. 11.87 ng/mL, p = 0.000). Furthermore, elevated eosinophil levels in asthma patients showed a strong correlation coefficient (0.307) with higher urinary bromotyrosine levels, indicating statistical significance (p = 0.005). Conclusion: The results of this study showed a significant difference in urinary bromotyrosine levels between asthmatic and non-asthmatic participant. There was a strong correlation between elevated eosinophil levels in asthma patients and increased urinary bromotyrosine levels.. Keywords: asthma, urinary bromotyrosine, eosinophils]]>
