Prevalence of diagnosed chronic immune thrombocytopenic purpura in the US: analysis of a large US claim database: a rebuttal

Abstract

To cite this article: Feudjo-Tepie MA, Robinson NJ, Bennett D. Prevalence of diagnosed chronic immune thrombocytopenic purpura in the US: analysis of a large US claim database: a rebuttal. J Thromb Haemost 2008; 6: 711-2. See also Segal JB, Powe NR. Prevalence of immune thrombocytopenia: analyses of administrative data. J Thromb Haemost 2006; 4: 2377-2383; Segal JB, Powe NR. Prevalence of diagnosed chronic immune thrombocytopenic purpura in the US: analysis of a large US claim database: reply to a rebuttal. This issue, pp 713. We read with interest the paper by Segal and Powe [1] on the prevalence of immune thrombocytopenic purpura (ITP). ITP is a disease caused by inadequate platelet production, as well as increased platelet destruction, and is traditionally categorized into acute and chronic forms. For the latter, thrombocytopenia needs to be present for at least 6 months [2]. In this paper, Segal and Powe refer to ITP as immune (rather than idiopathic) thrombocytopenia purpura. There is relatively little epidemiological evidence on chronic ITP, and its prevalence in the US is poorly documented. The paper by Segal and Powe is one of the first population-based studies of prevalence of ITP in the US that provides an estimate of chronic ITP (albeit informal). However, as the authors noted, there were some limitations in their study. Most of these were related to the limitations in the data source. In the analysis presented here, we aimed to estimate the diagnosed prevalence of ÔchronicÕ ITP in the US in 2005, using a large US claims data base. In particular, our analysis overcomes some of the main limitations in Segal and PoweÕs paper. (i) Segal and Powe used only one calendar year (2002) of data and identified potentially chronic ITP patients as those with at least two ITP ICD-9 codes (287.3), which were separated by at least 6 months. Therefore, a patient whose first ITP ICD-9 code occurred in the second half of 2002 had no chance of presenting a second code within the 2002 calendar year. Hence, as the authors pointed out, their estimation of the prevalence of ÔchronicÕ ITP in all people under 65 years (4.5 per 100 000) may be a considerable underestimate. (ii) Segal and PoweÕs estimation only includes patients under 65 years old. The increased risk of ITP with age is well documented [3-5] and excluding patients over 64 years of age would lead to an underestimate. We analyzed the Integrated Healthcare Information System (IHCIS) database, one of the largest US health care managed databases, fully de-identified, with over 70 million patients from more than 45 health plans. It covers 7 out of 10 census regions and contains patient demographics, age, gender and morbidity. Our patient population consisted of patients enrolled to one of the health plans before or any time between 2002 and 2006 with a continuous enrollment throughout the year 2004. Chronic ITP cases were defined as patients with at least two diagnoses (ICD-9 code 287.3) for primary thrombocytopenia separated by at least 6 months between 2002 and 2006....

Prevalence of Diagnosed Adult Immune Thrombocytopenia in the United Kingdom

“…where prevalence of chronic ITP increased with age and was higher among females. 19 This current analysis of GPRD data indicates the same pattern;…”

“…This was expected, given the female preponderance in ITP incidence. 17,28 In GPRD, the difference in prevalence between elderly female patients ≥65 years of age administrative data, [19][20][21] whereas cases within the present study were defined by electronic medical records. In addition, earlier data were from the US, whilst these were from the UK.…”

“…In published ITP incidence reports, estimates of adult ITP ranged from 1.6-3.9 per 100,000 adults per year in the United States (US), the United Kingdom (UK), and Japan. [13][14][15][16][17][18] Due to the chronic nature of adult ITP 12 and the consequent accumulation of cases in the population, available prevalence estimates are appreciably higher, 12,[19][20][21] ranging from a 1-year prevalence of 9.5 per 100,000 persons 21 to a high of 189.3 per 100,000 persons in a hospital-based study conducted in a US Veterans Administration patient population. 20 …”

Hospitalizations in pediatric patients with immune thrombocytopenia in the United States

“…Thrombocytopenia places patients at higher risk for minor and more serious bleeding, such as intracranial hemorrhage (ICH) [3]. Estimates of ITP incidence range between 2 and 5 cases per 100 000 per year in children who are younger than 15 years old [4][5][6]; prevalence estimates range between 4.1 and 12.6 cases per 100 000, depending on age, with a mean prevalence of approximately 7.2 cases per 100 000 in children younger than 18 years old [7][8]. Approximately 75% of pediatric ITP cases are newly diagnosed and persistent, with the remaining cases considered chronic [9][10][11][12].…”

Immune thrombocytopenia: Getting back to basics

“…Armed with their validated definition, the authors then set out to determine the frequency of ITP without restrictions, something that had previously only been done using databases of managed health care plans, limited to age groups or by point-prevalence questionnaires [18][19][20][21]. The authors found that the average annual prevalence of ITP was 8.1 per 100,000 children and 12.1 per 100,000 adults.…”