The correct answer is A, "Observe all steps for reprocessing," as this is the most important process for the infection preventionist (IP) to review when evaluating a third-party reprocessor for single-use devices. According to the Certification Board of Infection Control and Epidemiology (CBIC) guidelines, the reprocessing of single-use devices (SUDs) by third-party entities must adhere to stringent infection control standards to ensure they are safe for reuse and do not contribute to healthcare-associated infections (HAIs). Observing all steps—such as cleaning, disinfection, sterilization, packaging, and quality control—allows the IP to directly assess compliance with manufacturer instructions, regulatory requirements (e.g., FDA guidelines), and best practices (e.g., AAMI ST91) (CBIC Practice Analysis, 2022, Domain III: Infection Prevention and Control, Competency 3.3 - Ensure safe reprocessing of medical equipment). This hands-on evaluation is critical because any deviation in the reprocessing chain can compromise device sterility and patient safety.

Option B (review the facility's blueprints and policies) provides context about the physical layout and procedural framework, but it is a preliminary step that does not directly verify the reprocessing process’s effectiveness. Option C (ensure air and water cultures are performed regularly) is important for monitoring environmental contamination risks, particularly in sterile processing areas, but it is a supportive measure rather than the primary focus of evaluating the reprocessor’s core activities. Option D (obtain feedback from other IPs who use the reprocessor) offers valuable peer insights, but it is subjective and secondary to direct observation, which provides firsthand evidence of compliance and performance.

The priority on observing reprocessing steps aligns with CBIC’s emphasis on ensuring the safety and efficacy of reprocessed medical devices, a key responsibility for IPs when outsourcing to third-party reprocessors (CBIC Practice Analysis, 2022, Domain III: Infection Prevention and Control, Competency 3.5 - Evaluate the environment for infection risks). This process enables the IP to identify specific weaknesses, validate adherence to standards, and make informed decisions about the reprocessor’s suitability.