ABSTRACT:
In regulated pharmaceutical, medical device, and allied health manufacturing contexts, investigation systems and Corrective and Preventive Action (CAPA) processes are widely acknowledged as the most important quality control tools. Their main job is to turn quality failure incidents into long-lasting process enhancements that safeguard patients and guarantee ongoing regulatory compliance. Both systems continue to show basic performance limitations throughout the global industry despite decades of regulatory emphasis and the availability of well-validated methodological frameworks. This pattern has been documented in both published audit findings, regulatory warning letters, and quality management literature. This review article offers a thorough, humanised, and critically evaluated synthesis of the theoretical underpinnings, regulatory requirements, workflow architecture, primary systemic gaps, and evidence-based improvement strategies for investigation and CAPA systems. It was written especially for postgraduate students in pharmaceutical, food, and allied medicine disciplines. The article identifies six major investigation system deficiencies, including superficial root cause analysis, methodological inconsistency, data trending failures, and documentation weaknesses, along with six critical CAPA system gaps, including symptom-focused remediation, weak risk integration, poorly designed action plans, and inadequate effectiveness verification. These findings are based on peer-reviewed literature, ICH, FDA, EMA, WHO, and PIC/S regulatory guidance, as well as documented.