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When catheter-related infection is suspected, comparative cultures improve diagnostic clarity. The recommended approach is to obtain one set via the line (after rigorous hub antisepsis and appropriate discard per policy) and one set from a separate peripheral venipuncture site. Differential time-to-positivity or quantitative cultures can help determine whether the catheter is the source. Collect before starting antibiotics whenever possible and ensure adequate volume per bottle. Drawing both sets through the line (Option A) inflates contamination risk and cannot distinguish colonized catheter from true bacteremia. Using the same peripheral site for both sets (Option C) defeats the purpose of independent sampling. Cultures should be FIRST in order of draw (Option D is incorrect) to minimize additive carryover. Meticulous skin antisepsis, bottle stopper disinfection, correct fill volumes, and accurate time/site labeling are essential to reduce contamination and enhance yield—key competencies emphasized on certification exams.