Table 1. Characteristics of the Clostidioides difficile sentinel surveillance set up and patients included, by year, Denmark, 2016–2019.

Characteristic	2016		2017		2018		2019
Surveillance set up and results
Duration (spring and autumn)	2x2 weeks		2x1 month		2x1 month		2x1 month
Typing method	TRST		TRST		WGS/ST		WGS/ST
Toxin gene detection	PCR		PCR		WGS script		WGS script
Unique types/non-typable	54/6		75/22		77/7		76/9
%cdtAB negative	70.0		65.6		77.1		79.5
Simpson’s diversity index	0.89		0.90		0.92		0.93
Total number of samples (n = 2,692); unique patients (n = 2,594)a
Age group (years)	n	%	n	%	n	%	n	%
2–17	9	4.6	14	1.8	22	2.8	18	2.6
18–44	51	11.7	84	10.8	76	9.8	82	11.7
45–64	90	20.6	132	17.0	140	18.0	120	17.1
≥ 65	286	65.6	548	70.4	539	69.4	481	68.6
Female	%	p value	%	p value	%	p value	%	p value
	54.6	0.06	53.9	0.03	58.2	0.000003	54.2	0.03
Age in years and number of patients	n	Median age (range)	n	Median age (range)	n	Median age (range)	n	Median age (range)
Females	238	74 (3–95)	419	74(2–99)	452	73(2–97)	380	73 (3–103)
Males	198	70 (2–95)	359	73 (2–97)	325	72(2–95)	321	72 (2–94)
All	436	72 (2–95)	778	73 (2–99)	777	73(2–97)	701	73(2–103)

cdtAB: genes encoding C. difficile binary toxin; MiBa: Danish Microbiological Database; ST: sequence type, TRST: tandem repeat sequence type, WGS: whole genome sequencing.

^a All presented age distributions are based on total number of samples, i.e. some patients participated more than once (see Results).

Spring data collection took place between February and May and autumn data collection took place between October and November.