Long-Term Risk of Developing Immune Thrombocytopenia (ITP) or Another Blood Disorder in Adults Who Have Mildly Low Platelet Counts
A diagnosis of immune thrombocytopenia (ITP) is considered when a person presents with a persistent, isolated, and unexplained platelet count of less than 100,000/µL (normal reference range is 150,000-400,000). The long-term follow-up of individuals with a persistent, isolated, unexplained mild thrombocytopenia (PIMT) has not been well characterized. In this study, the investigators examined the likelihood that individuals with PIMT will go on to develop either ITP or another blood disorder.
To estimate the risk, individuals between the ages of 18-65 years who had been referred to a hematologist for PIMT in the Boston Massachusetts area from 1995-2004 were recruited using a patient registry. Individuals were not included in the study if they had a known secondary cause for their low platelet count. In total, 91 patients with PIMT of unknown cause were recruited for participation, in addition to 364 healthy controls (individuals of similar age and gender who did not have a low platelet count or any known risks for ITP or blood cancers). Data for participants were collected over a period of approximately 20 years following their diagnosis of PIMT.
Results revealed that 10% of individuals with PIMT had a diagnosis of ITP and 26% developed another blood disorder by 15 years. This corresponds to a 19-fold higher risk compared to age- and gender-matched healthy controls. The investigators also found that 13% of PIMT participants developed am autoimmune condition other than ITP vs 3% of health controls.
Among the small number of patients who reported significant bleeding, 26% had PIMT compared to 2% within the healthy control group and the risk for death of any cause was approximately 20% in the PIMT group, compared to 6% in the health control group.
Comments from PDSA Medical Advisors
This is the first systematic long-term study of individuals with platelet counts between 100-150,000 after an initial report by Dr. Roberto Stasi in 2006.
The results in the study summarized above suggest that it is likely that some of these individuals had very mild ITP that was not diagnosed as such until the platelet count fell below 100,000, the usual threshold used to make this diagnosis, while other were likely early in course of developing another blood disorder. The seriousness of the bleeding experienced by some of those with PIMT and the platelet counts when bleeding occurred were not well defined. The bottom line is that individuals with PIMT may have an increased risk to develop ITP or another blood disorder over time, and therefore ongoing clinical and laboratory monitoring is important.
Immune Thrombocytopenia and Pregnancy
This study examined the impact of pregnancy in women with immune thrombocytopenia (ITP) on the risk of developing worsening thrombocytopenia and the incidence of neonatal ITP (NITP) defined as a newborn having a platelet count below 50,000/µl.
The study included data from 131 pregnant women with ITP compared with 131 non-pregnant women from 32 centers within the French ITP reference network. Participants were followed for 15 months, which for the pregnant women meant they were followed during the pregnancy and 6 months after their infant was born.
ITP worsening was defined as either: (1) a new bleeding event, (2) severe thrombocytopenia (platelet count less than 30,000), or (3) the initiation or modification of an ITP treatment. No difference was found between the pregnant vs. non-pregnant participants in the incidence of severe thrombocytopenia or a new bleeding event. However, there was a higher rate of treatment initiation of modification in the pregnant ITP population, as expected. At the 6-month post-delivery timepoint, both the pregnant and non-pregnant cohorts had the same relative low rate of ITP worsening, which was approximately 17%.
When looking at recurring episodes of ITP worsening, pregnant ITP participants were more likely to have multiple events of severe thrombocytopenia and changes in treatment compared to non-pregnant ITP participants, although the rates of recurring bleeding events were similar between groups. This study also identified that the development of NITP was associated with: (1) a sibling with NITP and, (2) if the infant’s mother had a platelet count less than 50,000 within 3 months of delivery.
Comments from PDSA Medical Advisors
Many patients with ITP have a good deal of concern about getting pregnant, both in terms of the impact on their platelet count and the risk of delivering a child with severe thrombocytopenia and bleeding. This is one of many studies that indicate that pregnancy can be managed successfully in almost all women with ITP though frequent monitoring of the platelet count and alterations in management as needed. The comparison to women with ITP who do not become pregnant is reassuring in that only treatment modifications occur more frequently in women with ITP while pregnant. The study, like a number of previous ones, also provides reassurance that severe neonatal (newborn) thrombocytopenia does occur but is rare, though the risk is higher in those who previously delivered an affected child and, perhaps, those whose ITP is unstable at the time of delivery. Although the risk of adverse outcomes is low, women with ITP should be followed during pregnancy by experienced obstetricians and hematologists and later neonatologists, the latter especially in those at highest risk of delivering an affected neonate.