To evaluate HA-CDI and CA-CDI trends in Quebec, we performed a quasi-experimental study. We used prospectively collected data from the Quebec Health Ministry C. difficile Infection Surveillance Program (SPIN-CD), a mandatory surveillance program introduced in 2004. As of 2018, all 90 acute-care hospitals with ≥1,000 admissions annually participate in SPIN-CD. These hospitals, which represent 97% of all admissions in the province, use a centralized web portal to report HA-CDI incidence density, computed as the aggregate number of cases divided by the aggregate number of patient-days per 4-week period. CA-CDI incidence rates are expressed as the number of CA-CDIs/100,000 population as reported by the Quebec Institute of Statistics.
CDI is defined as diarrhea (≥3 unformed stools in <24 hours with symptoms lasting ≥24 hours) with no other etiology and either a positive toxigenic C. difficile test result or evidence of pseudomembranes during histopathologic or colonoscopic examination. A case is considered to be HA-CDI if symptoms appear ≥72 hours after admission or ≤4 weeks after discharge. A CA-CDI case is defined as illness in a hospitalized patient for whom symptoms developed within 72 hours of admission and who had not been hospitalized or received ambulatory care in the previous 4 weeks. Nonhospitalized CA-CDI case-patients and recurrences (i.e., new CDI episodes within 8 weeks of a previous episode) are not reportable to SPIN-CD. Definitions did not change during the study period. The type of laboratory assay used to detect C. difficile was at the discretion of each center.
To focus the analysis on the postepidemic period (April 2008–March 2015), we excluded data from the epidemic period (August 2004–March 2008). We used Poisson regression models on time series data, including trend and periodic seasonal terms to calculate incidence rate ratios (IRRs) with 95% CIs and to assess trends in CA-CDIs and HA-CDIs. We also used interrupted time series analysis with segmented regression because of a change in the level and trend in HA-CDI incidence rate from 2011 on. We compared the change in trends in HA-CDI and CA-CDI incidence by using Z-tests of the difference of the natural logarithm of incidence rates. We used SAS software version 9.3 (https://www.sas.com) for analyses and considered p<0.05 to be significant.
During the study period, a total of 28,854 cases of HA-CDI (84.5%) and CA-CDI (15.5%) were reported. The annual number of CA-CDI cases and the proportion of CDI cases that were reported as CA-CDI increased gradually from 510 (13.6% of HA-CDI) to 729 (17.8% of CA-CDI) cases (Table 1). Furthermore, the CA-CDI incidence rate increased ≈6.5% annually and overall significantly by 33.3%, from 0.51 to 0.68 cases/100,000 population (IRR per 4-week period 1.005, 95% CI 1.004–1.006; p<0.0001) (Figure 1). By contrast, the incidence of HA-CDI did not change significantly (IRR per 4-week period 1.000, 95% CI 0.999–1.000; p = 0.23). Accordingly, incidence rate trends for CA-CDI differed significantly from trends for HA-CDI (IRR 1.005, 95% CI 1.004–1.006; p<0.0001).
Incidence density of HA-CDIs and CA-CDIs per 4-week period, according to standardized surveillance definitions, Quebec, Canada, April 2008–March 2015. CDI, Clostridioides difficile infection; CA-CDI, community-associated CDI; HA-CDI, healthcare-associated CDI.
An inflection point in HA-CDI incidence in April 2011 was demonstrated by a significant decreasing change in trend (IRR 0.996, 95% CI 0.994–0.998; p = 0.001). By contrast, no concomitant change occurred in the trend of CA-CDI at the inflection point (Figure 2, Table 2).
Trends in incidence of HA-CDIs and CA-CDIs analyzed by using linear segmented regression (inflection point of HA-CDI in April 2011) per 4-week period, according to standardized surveillance definitions, Quebec, Canada, April 2008–March 2015. CDI, Clostridioides difficile infection; CA-CDI, community-associated CDI; HA-CDI, healthcare-associated CDI.
Emerging Infectious Diseases. 2020;26(6):1291-1294. © 2020 Centers for Disease Control and Prevention (CDC)