Of 103 NAAT-positive/CCNA-positive cases, 99 (96.1%) were primary CDI cases, and of the 49 NAAT-positive/CCNA-negative cases, 10 (20.4%) were primary CDI cases (7 had PMC and 3 had a specimen collected during the 90-day follow-up period that was NAAT-positive/CCNA-positive), for a total of 109 study-identified primary CDI cases. The gene discussed is CCNA2; the disease is clostridium difficile infection.