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. 2025 Aug 21;30(33):2400801. doi: 10.2807/1560-7917.ES.2025.30.33.2400801

Table 3. Characteristics of patients identified by different combinations of the International Statistical Classification of Diseases and Related Health Problems 10th Revision (ICD-10) diagnosis codes, for case definitions 1 to 6, Denmark, week 1 2022–week 52 2023 (n = 6 case definitions).

Characteristics Case definition
CD1 CD2 CD3 CD4 CD5 CD6
Total 113,313 5,207 9,588 20,353 75 12,787
Age group (years) n % n % n % n % n % n %
0–4 4,048 3.6 3,900 74.9 4,448 46.4 0 0.0 1 1.3 779 6.1
5–14 1,012 0.9 107 2.1 910 9.5 1 0.0 0 0.0 377 2.9
15–29 4,080 3.6 37 0.7 1,605 16.7 3 0.0 7 9.3 806 6.3
30–64 22,619 20.0 295 5.7 1,617 16.9 3,711 18.2 33 44.0 4,091 32.0
65–79 39,892 35.2 464 8.9 649 6.8 10,515 51.7 25 33.3 4,545 35.5
≥80 41,662 36.8 404 7.8 359 3.7 6,123 30.1 9 12.0 2,189 17.1
Length of stay (days) Median IQR Median (IQR) Days (n) Median (IQR) Days (n) Median (IQR) Days (n) Median (IQR) Days (n) Median (IQR)
Overall 4.1 2.1–7.2 1.9 1.0–3.9 1.1 0.7–2.2 3.6 1.9–6.1 20.2 8.9–36.0 3.1 1.0–9.3
Intensive care treatment n % n % n % n % n % n %
Patients receiving ICT 10,520 9.3 778 14.9 1,114 11.6 4,009 19.7 65 86.7 7,315 57.2
Mortality n % n % n % n % n % n %
All mortality 13,100 11.6 77 1.5 75 0.8 2,033 10.0 29 38.7 2,552 20.0
In-hospital mortality 7,667 6.8 30 0.6 43 0.4 1,193 5.9 26 34.7 2,089 16.3
SARS-CoV-2 n % n % n % n % n % n %
Tested 93,227 82.3 3,702 71.1 5,268 54.9 16,014 78.7 46 61.3 5,718 44.7
Positive
(n and % of tested)
30,001 32.2 77 2.1 265 5.0 373 2.3 2 4.3 194 3.4
Influenza virus n % n % n % n % n % n %
Tested 79,275 70.0 3,935 75.6 4,966 51.8 14,521 71.3 40 53.3 4,424 34.6
Positive
(n and % of tested)
7,429 9.4 19 0.5 127 2.6 174 1.2 1 2.5 39 0.9
RSV n % n % n % n % n % n %
Tested 40,771 36.0 3,784 72.7 3,838 40.0 6,976 34.3 22 29.3 2,161 16.9
Positive,
(n and % of tested)
2,156 5.3 1,828 48.3 415 10.8 337 4.8 0 0.0 181 8.4

CD: case definition; ICT: intensive care treatment; IQR: interquartile range, RSV: respiratory syncytial virus.