Table 2. Incidence of Inpatient or Outpatient Venous Thromboembolism in Patients With Bullous Pemphigoid (BP) vs Those Without BP.

Variable	BP				Non-CISD				BP vs non-CISD, hazard ratio (95% CI)
	Patients, No.	Person-time in 1000 person-years	Events, No.	Incidence rate per 1000 person-years	Patients, No.	Person-time in 1000 person-years	Events, No.	Incidence rate per 1000 person-years
VTE, inpatient or outpatient with treatment (primary analysis) a
Unmatched
Total patients with BPb	2654	7417	63	8.49	26 814	76 010	133	1.75	4.85 (3.60-6.55)
Age 18-49 y	140	437	1	2.29	9802	25 986	18	0.69	3.17 (0.42-23.73)
Age ≥50 y	2514	6980	62	8.88	17 011	50 022	115	2.30	3.84 (2.82-5.23)
Age 50-74 yc	1023	3150	25	7.94	12 436	36 518	73	2.00	3.96 (2.51-6.24)
Age ≥75 yc	1491	3831	37	9.66	4575	13 504	42	3.11	3.04 (1.95-4.73)
Without immunomodulator use	2272	6291	54	8.58	26 365	74 825	132	1.76	4.85 (3.54-6.66)
1:1 PS matchedd
Total patients with BP	1863	5356	36	6.72	1863	5661	17	3.00	2.24 (1.26-3.98)
Age 18-49 y	111	349	0	0.00	111	327	0	0.00	NA
Age ≥50 yc	1742	5006	34	6.79	1742	5385	20	3.71	1.82 (1.05-3.16)
Age 50-74 yc	768	2378	14	5.89	768	2357	7	2.97	2.00 (0.81-4.96)
Age ≥75c	935	2525	18	7.13	935	2650	12	4.53	1.55 (0.75-3.23)
Without immunomodulator usee	1663	4761	34	7.14	1663	5106	18	3.53	2.01 (1.13-3.56)
VTE, inpatient (secondary analysis) f
Unmatched
Total patients with BP	2654	7499	35	4.67	26 814	76 209	65	0.85	5.48 (3.63-8.26)
Age 18-49 y	140	444	0	0.00	9802	26 026	7	0.27	NA
Age ≥50 y	2514	7055	35	4.96	17 011	50 180	58	1.16	4.28 (2.81-6.51)
Age 50-74 y	1023	3187	16	5.02	12 436	36 611	34	0.93	5.44 (3.00-9.87)
Age ≥75 y	1491	3868	19	4.91	4575	13 569	24	1.77	2.74 (1.50-5.00)
Without immunomodulator use	2272	6357	32	5.03	26 365	75 022	65	0.87	5.80 (3.80-8.86)
1:1 PS matched
Total patients with BP	1863	5389	22	4.08	1863	5671	13	2.29	1.77 (0.89-3.51)
Age 18-49 y	111	349	0	0.00	111	327	0	0.00	NA
Age ≥50 y	1742	5038	22	4.37	1742	5417	10	1.85	2.33 (1.10-4.93)
Age 50-74 y	768	2387	11	4.61	768	2366	4	1.69	2.74 (0.87-8.60)
Age ≥75 y	935	2551	10	3.92	935	2672	6	2.25	1.67 (0.61-4.62)
Without immunomodulator use	1663	4795	24	5.00	1663	5127	12	2.34	2.11 (1.06-4.23)

Abbreviations: CISD, chronic inflammatory skin disease; IMD, immune-modulating drug; NA, not applicable; PS, propensity-score; VTE, venous thromboembolism.

^a We identify incident VTE, deep venous thrombosis or pulmonary embolism, events during all available follow-up time. We defined VTE as either a hospitalization with a primary discharge diagnosis of VTE, or an outpatient visit with a diagnosis of VTE followed by initiation of an anticoagulant within 7 days or hospitalization for VTE within 7 days.

^b Although the risk-set-sampling identified 2991 and 29 910 patients, respectively, further exclusions and censoring on day 0 resulted in 2654 patients with BP and 26 814 comparators.

^c These are not mutually exclusive age categories, in that the patients in the age 75 years or older subgroup are also included in the age 50 years or older subgroup. PS matching is then conducted in each subgroup of age separately, as such the numbers may not add up to the age 50 years or older group.

^d Patients were 1:1 propensity-score matched (0.02 caliper) on more than 60 VTE risk factors, severity markers, systemic corticosteroid use, treatments, and other patient characteristics. See eTables 1 and 2 in Supplement 1 for a detailed list of all adjustment variables.

^e In a subgroup analysis we excluded patients using systemic immunomodulating agents defined as patients receiving treatment with nonbiologic immunomodulatory agents (methotrexate, cyclosporine, mycophenolate mofetil, azathioprine, sulfasalazine, or leflunomide), biologic immunomodulatory agents (dupilumab, risankizumab-rzaa, tildrakizumab, ixekizumab, secukinumab, guselkumab, ustekinumab, abatacept, adalimumab, etanercept, golimumab, certolizumab, infliximab, rituximab, anakinra, or tocilizumab), and targeted synthetic immunomodulatory agents (tofacitinib or baricitinib), not including systemic corticosteroids.

^f For a more specific but less sensitive definition, we limited the secondary outcome to include only inpatient events, defined as hospitalization with a primary discharge diagnosis of deep venous thrombosis or pulmonary embolism.