A rapid and accurate diagnosis of Clostridium difficile infection (CDI) is essential for patient management and implementation of infection control measures. During a prospective time-series study, we compared the impact of three different diagnostic strategies on patient care. Each strategy was tested during a 3-month period: P1 (diagnosis based on the stool cytotoxicity assay and the toxigenic culture), P2 (diagnosis based on PCR) and P3 (two-step algorithm based on glutamate dehydrogenase detection followed by nucleic acid amplification test). The following criteria were used to assess the quality of patient management: (i) time for result reporting, (ii) frequency of repeat testing within 7 days, (iii) time elapsed between stool collection and beginning of treatment for patients with CDI, and (iv) frequency of empirical treatment for patients without CDI. Of 1122 stool samples (P1 n = 359, P2 n = 374, P3 n = 389), 36 (10.0%), 47 (12.3%) and 48 (12.3%) were positive for C. difficile during P1, P2 and P3, respectively. The time for reporting of a positive or a negative result was significantly shorter and the frequency of redundant stool samples within 7 days was lower during P2 and P3 than during P1. Patients with CDI were specifically treated with vancomycin or metronidazole earlier during P2 and P3 than patients from P1 (0.5 ± 0.5 days and 1.0 ± 1.8 days vs. 2.0 ± 1.7 days). The empirical therapy among patients without CDI decreased from 13.6% during P1 to 6.4% during P2 and 5.6% during P3. A rapid CDI diagnosis impacts positively on patient care.