Healthcare resource utilization among patients with cold agglutinin disease in Denmark

Figures & data

Figure 1. Patient flow diagram. Danish health registries (1999–2016). Abbreviations. CAD, Cold agglutinin disease; DNPR, Danish National Patient Registry.

Table 1. Demographic and clinical baseline characteristics of the Danish CAD cohort and matched comparison cohort: Danish health registries (1999–2016).

	CAD cohort (N = 104)		Matched comparison cohort (N = 1003)
	n	%	n	%
Sex
Male	49	47.1	479	47.8
Female	55	52.9	524	52.2
Age at index date, years
18–59	18	17.3	194	19.3
60–69	23	22.1	219	21.8
70–79	40	38.5	368	36.7
≥80	23	22.1	222	22.1
Age at index date, years
Mean (SD)	70.5 (11.8)		70.1 (11.9)
Year of diagnosis/index date
1999–2004	10	9.6	100	10.0
2005–2008	18	17.3	180	17.9
2009–2012	36	34.6	342	34.1
2013–2016	40	38.5	381	38.0
CCI score
0	38	36.5	380	37.9
1–2	42	40.4	420	41.9
≥3	24	23.1	203	20.2

Abbreviations. CAD, cold agglutinin disease; CCI, Charlson Comorbidity Index; SD, standard deviation.

Table 2. Total and CAD-related healthcare resource utilization of the Danish CAD and matched comparison cohorts within 12 months months after the index date.

	CAD cohort (N = 104)	Matched comparison cohort (N = 1003)	OR/RR (95% CI)	p-value
Inpatient hospitalizations
Total utilization
Number of patients n (% of cohort)	55 (52.8)	227 (22.6)	3.9 (2.5–6.0)^a	<.0001
No. of admissions per patient median (IQR)	1 (0–3)	0 (0–0)	5.1 (3.6–7.3)^b	<.0001
Hospital days per patient median (IQR)	1.5 (0–14)	0 (0–0)	N/A	.001^c
CAD-related utilization
Number of patients n (% of cohort)	34 (32.7)	36 (3.6)	15.3 (8.3–28.2)^a	<.0001
No. of admissions per patient median (IQR)	0 (0–1)	0 (0–0)	40.1 (18.2–88.6)^b	<.0001
Hospital days per patient median (IQR)	0 (0–6.5)	0 (0–0)	N/A	.331^c
Outpatient clinic visits
Total utilization
Number of patients n (% of cohort)	99 (95.2)	590 (58.8)	17.2 (6.8–43.1)^a	<.0001
No. of admissions per patient median (IQR)	10 (4.5–19.5)	1 (0–4)	5.3 (4.1–6.8)^b	<.0001
CAD-related utilization
Number of patients n (% of cohort)	57 (54.8)	93 (9.3)	36.4 (18.2–72.7)^a	<.0001
No. of admissions per patient median (IQR)	2 (0–9)	0 (0–0)	180.9 (88.9–368.1)^b	<.0004
Emergency room visits (total)
Number of patients n (% of cohort)	20 (19.2)	137 (13.7)	1.4 (0.8–2.4)^a	.231
No. of admissions per patient median (IQR)	0 (0–0)	0 (0–0)	2.0 (1.3–3.1)^b	.008
Transfusion use (total)
Number of patients n (% of cohort)	45 (43.3)	13 (1.3)	93.0 (33.3–259.8)^a	<.0001
No. of transfusion days for patients with transfusion median (IQR)	4 (1.0–7.0)	2 (2.0–13.0)	N/A	N/A
Expensive drug use (total)
Number of patients n (% of cohort)	11 (10.6)	12 (1.2)	12.8 (4.9–33.6)^a	<.0001
No. of treatment days for patients with drug use median (IQR)	2 (1–7)	3 (1.5–8)	N/A	N/A

Danish health registries (1999–2016).

Abbreviations. CAD, Cold agglutinin disease; CI, Confidence interval; IQR, Interquartile range; N/A, Not applicable; OR, Odds ratio; RR, Rate ratio.

^aOR in the CAD cohort versus the comparison cohort estimated with conditional logistic regression (e.g. OR = 3.9 means that the odds of inpatient hospitalization are 3.9 times higher for a patient with CAD compared with comparison cohort members selected from the general population).

^bRR in the CAD cohort versus the comparison cohort estimated with a negative binomial mixed model (e.g. RR = 5.1 means that the rate of inpatient hospitalizations is 5.1 times for a patient with CAD compared with comparison cohort members selected from the general population).

^cZero-inflated negative binomial model, significance test for the negative binomial part of the model.

Table 3. Total and CAD-related healthcare resource utilization of the Danish CAD and matched comparison cohorts within 6 months months prior to the index date.

	CAD cohort (N = 104)	Matched comparison cohort (N = 1003)	OR/RR (95% CI)	p-value
Inpatient hospitalizations
Total utilization
Number of patients n (% of cohort)	32 (30.8)	126 (12.6)	3.1 (1.9–5.1)^a	.0002
No. of admissions per patient median (IQR)	0 (0–1)	0 (0–0)	3.7 (2.3–5.9)^b	<.0001
Hospital days per patient median (IQR)	1.5 (0–14)	0 (0–0)	N/A	.115^c
CAD-related utilization
Number of patients n (% of cohort)	19 (18.3)	29 (2.9)	8.7 (4.2–17.9)^a	<.0001
No. of admissions per patient median (IQR)	0 (0–0)	0 (0–0)	15.0 (7.3–30.9)^b	<.0001
Hospital days per patient median (IQR)	0 (0–0)	0 (0–0)	N/A	.865^c
Outpatient clinic visits
Total utilization
Number of patients n (% of cohort)	83 (79.8)	469 (46.8)	6.4 (3.6–11.3)^a	<.0001
No. of admissions per patient median (IQR)	3 (1–6)	0 (0–2)	3.3 (2.5–4.3)^b	<.0001
CAD-related utilization
Number of patients n (% of cohort)	48 (46.2)	87 (8.7)	22.9 (12.1–43.3)^a	<.0001
No. of admissions per patient median (IQR)	0 (0–3)	0 (0–0)	52.3 (28.4–96.4)^b	<.0002
Emergency room visits (total)
Number of patients n (% of cohort)	20 (19.2)	51 (5.1)	4.2 (2.4–7.3)^a	<.0001
No. of admissions per patient median (IQR)	0 (0–0)	0 (0–0)	4.8 (2.9–8.0)^b	<.0001
Transfusion use (total)
Number of patients n (% of cohort)	21 (20.2)	13 (1.3)	26.6 (10.6–66.9)^a	<.0001
No. of transfusion days for patients with transfusion median (IQR)	2 (1.0–3.0)	2 (2.0–4.0)	N/A	N/A
Expensive drug use (total)
Number of patients n (% of cohort)	≤5	9 (0.9)	4.5 (1.3–15.8)^a	.017
No. of treatment days for patients with drug use median (IQR)	2 (2–4)	4 (2.5–14)	N/A	N/A

Danish health registries (1999–2016).

Abbreviations. CAD, Cold agglutinin disease; CI, Confidence interval; IQR, Interquartile range; N/A, Not applicable; OR, Odds ratio; RR, Rate ratio.

^aOR in the CAD cohort versus the comparison cohort estimated with conditional logistic regression (e.g. OR = 3.9 means that the odds of inpatient hospitalization are 3.9 times higher for a patient with CAD compared with comparison cohort members selected from the general population).

^bRR in the CAD cohort versus the comparison cohort estimated with a negative binomial mixed model (e.g. RR = 5.1 means that the rate of inpatient hospitalizations is 5.1 times for a patient with CAD compared with comparison cohort members selected from the general population).

^cZero-inflated negative binomial model, significance test for the negative binomial part of the model.

Data availability statement

Data used in this analysis is protected by the Danish government and is not available.