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, 14, 80-87

Chronic Immune Thrombocytopenia in Denmark, Sweden and Norway: The Nordic Country Patient Registry for Romiplostim


Chronic Immune Thrombocytopenia in Denmark, Sweden and Norway: The Nordic Country Patient Registry for Romiplostim

Christian Fynbo Christiansen et al. EClinicalMedicine.


Background: Population-based cohorts of immune thrombocytopenia (ITP) are useful for understanding occurrence, clinical characteristics and long-term clinical course. This paper describes the content of the Nordic Country Patient Registry for Romiplostim (NCPRR) and provides prevalence and incidence estimates of chronic ITP (cITP).

Methods: The NCPRR, a cohort study established in 2009, includes all adult (≥ 18 years) patients in Denmark, Sweden and Norway with cITP (defined as ITP lasting > 12 months and platelet count < 100 × 109/L), combining data from national health registries and medical records. The NCPRR currently includes prevalent cITP patients diagnosed before 2009 and incident cITP patients diagnosed during 2009-2016. The registry obtains clinical information for cITP patients, including comorbidities, treatments, laboratory values, and complete follow-up for various outcomes.

Findings: The NCPRR currently includes 3831 patients with cITP (1258 prevalent; 2573 incident). In 2009, the prevalence of registered cITP was 10 · 0/100,000 (95%CI:9 · 1-11 · 0) adult persons in Denmark and 10 · 7/100,000 (95% CI: 9 · 9-11 · 4) adults in Sweden. During 2009-2016, the incidence rates of cITP per 100,000 person-years were 2 · 8 (95%CI: 2 · 6-3 · 0), 1 · 8 (95%CI: 1 · 7-1 · 9) and 2 · 1 (95%CI: 1 · 9-2 · 2) in Denmark, Sweden and Norway, respectively. Fifty-eight percent of cITP patients were women. At NCPRR inclusion, 30.2% were aged ≥ 70 years, 23% had a platelet count < 50 × 109/L, 17.4% were splenectomized, 41% had prior ITP therapy, and 8.6% had severe comorbidity.

Interpretation: The NCPRR provides population-based data on the epidemiology and characteristics of almost 4000 cITP patients and is a valuable resource for research.

Funding: This study was partly funded by a research grant from Amgen to Aarhus University.

Keywords: Bone marrow fibrosis; Epidemiology; Immune thrombocytopenia; Incidence; Population-based; Prevalence; Registry.


Fig. 1
Fig. 1
Patient flow chart of the Nordic cohort of adult patients with chronic ITP requiring health care in Denmark, Sweden and Norway, 2009–2016. *Two or more ITP diagnoses more than 6 months apart between January 1, 1996 and December 31, 2016, among patients alive on April 1, 2009. †After exclusion of patients with a patient registry diagnosis of potential other causes of thrombocytopenia. ‡Restricted to patients with a hospital contact for ITP between April 1, 2009 and December 31, 2016, because these patients are considered to have been actively followed during the study period. Hospital contacts include hospital admissions, outpatient specialist clinic visits, and emergency room visits. §Including 123 patients in non-participating hospitals and 257 patients with records from smaller hospitals with few patients diagnosed with ITP and without hematological services. The number of unavailable records was 299 in Sweden, 33 in Denmark and 48 in Norway. ||ITP could not be confirmed by record review because of secondary thrombocytopenia, primarily due to connective tissue disease, myelodysplatic syndrome, myelofibrosis, gestational thrombocytopenia, or thrombotic thrombocytopenic purpura. ¶At least one documented platelet count < 150 × 109/L is required, but may not be available if it was measured several years before study inclusion.
Fig. 2
Fig. 2
Prevalence (per 100,000 inhabitants) of immune thrombocytopenia in Denmark and Sweden by age group and sex.
Fig. 3
Fig. 3
Incidence rate (per 100,000 person-years) of immune thrombocytopenia in Denmark, Sweden and Norway by age group and sex.

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