Instruments for Assessing Spirituality in Patients with Chronic or Advanced Illnesses: A Systematic Review of the Last 15 Years

Background/Objectives: Spirituality is a key component of coping and well-being in chronic and advanced illness, yet its assessment remains inconsistent across clinical settings. To identify, classify, and critically analyze the most commonly used and validated instruments for measuring spirituality in clinical contexts, focusing on their ability to assess the current spiritual state from a multidimensional perspective (cognitive, behavioral, and affective expressions). Methods: A systematic literature review was conducted using PubMed, Scopus, and Web of Science (2011–2024). Inclusion criteria targeted validation studies of instruments assessing spirituality in adults with chronic or advanced illnesses or in palliative care. A dual conceptual–functional classification was applied, and a custom scoring system was developed to evaluate psychometric quality. Contamination and tautological aspects were also examined. Results: Forty-three instruments were identified across 42 studies. Of these, 93.02% included cognitive, affective, and behavioral dimensions. Most were validated in oncology or chronic disease populations. Content validity and internal consistency were the most reported psychometric properties; responsiveness was rarely evaluated. Conclusions: The available instruments reflect several conceptual and functional approaches. The classification proposed in this review provides practical guidance for selecting scales according to specific clinical goals and settings, supporting the evaluation of the current spiritual state and the integration of spirituality into healthcare practice. Further research is recommended to develop culturally sensitive and responsive instruments suitable for diverse clinical contexts.