To translate, culturally adapt, and psychometrically validate the Farsi version of the Bladder Pain/Interstitial Cystitis Symptom Score (BPIC-SS) for use in Farsi-speaking patients with interstitial cystitis/bladder pain syndrome (IC/BPS).

The BPIC-SS was translated into Farsi using a forward–backward translation method followed by an expert panel review. A total of 100 clinically diagnosed IC/BPS patients completed the Farsi BPIC-SS. For psychometric evaluation, we included descriptive analysis, internal consistency (Cronbach’s alpha), test–retest reliability (intraclass correlation coefficient; ICC) in a subgroup of 18 patients, and exploratory factor analysis (principal component analysis with Varimax rotation). Sampling adequacy was assessed using the Kaiser–Meyer–Olkin (KMO) measure and Bartlett’s test of sphericity and we examined the floor and ceiling effects.

All patients demonstrated complete response rates with adequate variability. Mean item scores ranged from 2.17 to 2.81 (0–4 scale), and the pain item mean was 6.34 ± 1.88 (0–10 scale), without floor or ceiling effects. Internal consistency was acceptable (Cronbach’s alpha = 0.716; standardized alpha = 0.741). Intraclass correlation coefficient for test–retest reliability ICC = 0.788( 95% CI: 0.612–0.907; p < 0.001), and the spearman–Brown coefficient for split-half reliability was 0.994. Factor analysis supported a two-factor structure explaining 63.7% of the variance, with Factor 1 representing pain/pressure and Factor 2 representing frequency/nocturia (KMO = 0.652; Bartlett’s χ² = 352.16, p < 0.001).

The findings indicate that the Farsi BPIC-SS demonstrates satisfactory internal consistency and reproducibility, comparable to previously validated versions of IC/BPS symptom questionnaires. The identified two-factor structure aligns with the known clinical domains of IC/BPS, namely pain-related symptoms and urinary frequency, supporting construct validity. The absence of floor and ceiling effects suggests adequate sensitivity across a broad range of symptom severity. Although the KMO value was modest, it remained within an acceptable range for factor analysis, and the explained variance further supports the robustness of the scale. Overall, these results indicate that the instrument reliably captures the multidimensional symptom profile of IC/BPS in Farsi-speaking populations.

The Farsi BPIC-SS is a valid and reliable instrument for assessing symptom severity in Farsi-speaking patients with IC/BPS. Its use can enhance clinical evaluation, facilitate inclusion of Farsi-speaking populations in research, and support standardized symptom assessment across international settings. Further studies should investigate responsiveness and establish the diagnostic cut-off values.