Interstitial Cystitis/Bladder Pain Syndrome (IC/BPS) is a chronic condition requiring validated assessment tools for effective clinical and research use. The Apollo Clinical Scoring System is a novel questionnaire that comprehensively evaluates pain, urinary symptoms, sexual dysfunction, and psychological impact. This study aimed to translate and validate the Persian version of this instrument. We aimed to evaluate the validity and reliability of the Persian translation of the Apollo Clinical Scoring System in an Iranian IC/BPS population.

This methodological study included 100 patients with ESSIC-confirmed IC/BPS. The questionnaire was translated using the forward-backward method. Face and content validity were assessed using Impact Score, Content Validity Ratio (CVR), and Content Validity Index (CVI). Construct validity was evaluated using Exploratory Factor Analysis (EFA) with Principal Component Analysis (PCA). Reliability was assessed using Cronbach's Alpha (internal consistency) and Intraclass Correlation Coefficient (ICC) for test-retest stability over 15 days.

All items demonstrated acceptable face validity (Impact Score ≥ 0.75). CVR and CVI values exceeded thresholds (CVR > 0.62; CVI > 0.79). The Kaiser-Meyer-Olkin (KMO) measure was 0.679, and Bartlett's Test of Sphericity was significant (p < 0.001), supporting factor analysis. PCA revealed two components explaining 64.04% of total variance: "Urinary Urgency and Frequency" (40.20%) and "Symptom Impact and Discomfort" (23.84%). Cronbach's Alpha was 0.725, indicating acceptable internal consistency. The ICC for average measures was 0.765 (95% CI: 0.618–0.871), demonstrating good test-retest reliability.

The findings demonstrate that the Persian version of the Apollo Clinical Scoring System possesses satisfactory psychometric properties for use in patients with IC/BPS. The strong face and content validity indicators (high Impact Score, CVR, and CVI) confirm that the translated items are both relevant and culturally appropriate. Construct validity was supported by factor analysis, which identified a coherent two-factor structure capturing both symptom severity (urgency/frequency) and the broader impact of the disease, aligning well with the multidimensional nature of IC/BPS.

Reliability analysis further supports the robustness of the instrument. The Cronbach’s alpha indicates acceptable internal consistency, suggesting that the items measure a unified construct while still capturing different symptom domains. Additionally, the ICC reflects good test–retest reliability, indicating stability of responses over time.

Overall, these results suggest that the questionnaire is a reliable and reasonably valid tool for clinical and research applications. However, the moderate KMO value and the extraction of only two components may indicate some limitations in capturing the full complexity of IC/BPS, warranting further validation in larger and more diverse populations.

The Persian version of the Apollo Clinical Scoring System demonstrates good reliability and acceptable validity, making it a suitable tool for assessing IC/BPS symptoms in Iranian patients. This instrument facilitates standardized assessment and cross-cultural comparisons in clinical practice and research.