Reviewed diagnosis of primary and secondary immune thrombocytopenic purpura in 79 adult patients hospitalized in 2000-2002.

Despite the accepted distinction between primary and secondary immune thrombocytopenic purpura (ITP), a systematic analysis of the incidence of secondary ITP is not available. The present study was aimed at verifying the frequency and, consequently, the approximate rates of prevalence and incidence of secondary ITP and analysing its clinical and laboratory characteristics in patients needing ordinary hospital treatment for ITP. The study was based on 79 consecutive, adult ITP patients admitted to three Italian hospitals in 2000-2002. Using data collected in a previous study on the appropriateness of hospital management of ITP, we evaluated the frequency of secondary ITP, with the diagnosis formulated on the basis of new acquisitions, derived its rates of prevalence and incidence, and examined the available clinical and laboratory parameters. At our case review, a diagnosis of secondary ITP could be formulated in 38% of the 79 patients. This frequency was significantly higher than that determined at the time the patients were discharged from hospital (13.9%) (P = 0.000). The derived rates of prevalence and incidence of secondary ITP in the general population were, respectively, 2.3 and 1.23 per 100 000 inhabitants per year. In comparison with patients with primary ITP, those with a secondary form more frequently had spleen enlargement (P = 0.000), hepatomegaly (P = 0.001) and lower haemoglobin values (P = 0.005). The high frequency of secondary ITP must be mainly attributed to the currently available knowledge about the nature of some forms of ITP. Particular contributors to the high frequency were cases secondary to infections and those observed in patients who had undergone bone marrow or solid organ transplantation. Some clinical and laboratory alterations appear to be more frequent in secondary ITP than in primary ITP. However, the importance that the identification of particular forms of ITP, such as those secondary to Helicobacter pylori or hepatitis C virus infections, has on the choice of treatment suggests that these conditions must be ascertained independently of the presence or absence of clinical and laboratory alterations.