Abstract Introduction Clopidogrel is recommended as an alternative to Acetyl Salicylic Acid (ASA), the first-line drug for secondary stroke prevention. Clopidogrel resistance in Indonesia is reportedly 15.8%. The Stent Thrombosis in Belgium (STIB) is a scoring system proposed to assess clopidogrel resistance which has not been tested for the reliability in Indonesian population. Objectives The objective of the study is to test the reliability of the STIB scoring and modified-STIB scoring system in Indonesian population. Methods This study was conducted cross-sectionally in Dr. Cipto Mangunkusumo Hospital and Universitas Indonesia Hospital from January 2020 to December 2021. Laboratory examinations of human CYP450 concentration in blood plasma from 112 subjects were carried out using the ELISA method. The clopidogrel resistance test was carried out using the VerifyNow method. Results Out of 112 ischemic stroke patients in this study, 14.3% of them did not respond to clopidogrel. Cross-tabulation between the STIB score and clopidogrel resistance showed significant results (p < 0.05) on the Hb variable and a combination of two or three factors involving Hb levels. Both Hb and CYP450 levels can be independent factors predicting clopidogrel resistance. Once combined, the Hb and CYP450 cutoff levels of 458.9 pg/mL had a sensitivity of 100% with a specificity of 30.2%. Conclusions STIB scoring system did not prove to be reliable in screening for Clopidogrel resistance in Indonesian population. The modified STIB scoring system proposed in this study showed a promising result. Further research with larger population should be conducted.