Development and validation of the Clinical Nursing Knowledge Questionnaire-15 (CNKQ-15) for assessing contraceptive knowledge among nurses

Background: Deficiencies in contraceptive knowledge among healthcare professionals persist worldwide, while existing assessment tools lack rigorous psychometric validation and standardized interpretation. Given nurses' central role in contraceptive counseling, a robust, profession-specific instrument is needed to accurately identify knowledge gaps and guide targeted training to improve clinical practice. Objective: To develop and psychometrically validate the Contraception Nursing Knowledge Questionnaire (CNKQ-15) in order to provide a standardized tool for assessing contraceptive knowledge and identifying training needs among nursing professionals. Design: A methodological study conducted in two phases: qualitative instrument development and cross-sectional psychometric evaluation. Settings: A nationwide study conducted in Spain between February and April 2025. Data collection was distributed digitally through the General Council of Nursing and provincial official nursing colleges. Participants: A total of 1123 actively practicing nursing professionals (including generalist nurses and specialized nurses). Methods: Content validity was assessed by a multidisciplinary expert panel using Aiken's V index. Psychometric evaluation included item difficulty and discrimination analysis, known-groups discriminant validity (comparing specialists in Obstetrics and Gynecology with non-specialized nurses), and test-retest reliability evaluated in a subsample of 100 participants over a 14-day interval. Standardized cut-off points were also established. Results: The final sample included 1123 nursing professionals, predominantly women (90.5%), with a mean age of 38.3 years (SD = 10.3). Most participants reported no specialization (58.2%), while 23.5% specialized in Obstetrics and Gynecology. The CNKQ-15 showed adequate item difficulty indices (0.30-0.94) and demonstrated strong discriminant validity, effectively distinguishing between professionals specialized in Obstetrics and Gynecology and those without specialization (mean scores 12.7 vs. 9.9; p < 0.001). Test-retest reliability was excellent, with an intraclass correlation coefficient of 0.85 (95% CI [0.77-0.91]). According to the established cut-off points, 48.3% of participants exhibited null or insufficient knowledge of contraception, 30.1% achieved only a minimal level, and fewer than one in five demonstrated good or very good knowledge. This proportion of inadequate knowledge increased to 59.3% among nurses without specialization in Obstetrics and Gynecology. Conclusions: The CNKQ-15 shows adequate content validity, discriminant validity, and reliability. Its standardization allows the accurate identification of knowledge gaps among nursing professionals, including midwives, and offers a practical tool for evaluating contraceptive training and guiding targeted educational interventions. Social media abstract: The newly validated CNKQ-15 robustly assesses contraceptive knowledge in nurses and midwives, identifying critical gaps. @cris90due.