Which of the following is NOT a commonly used classification system in healthcare?

HIMSS, or the Healthcare Information and Management Systems Society, is not a classification system used to categorize medical diagnoses or procedures. Instead, HIMSS is a global organization focused on improving healthcare through information technology and management systems. They provide resources, education, and advocacy for healthcare organizations but do not offer a classification system like ICD, CPT, or HCPCS.

In contrast, ICD (International Classification of Diseases), CPT (Current Procedural Terminology), and HCPCS (Healthcare Common Procedure Coding System) are all established classification systems. ICD is predominantly used for coding diagnoses and diseases, CPT focuses on procedural coding, and HCPCS includes codes for various medical services and items not covered by CPT. Thus, HIMSS stands apart as a professional organization rather than a classification system, making it the correct answer to the question.