Page 196 - 2020_11-Haematologica-web

Letters to the Editor
Figure 2. Frequency of response and bleeding in primary immune thrombocytopenia. Center column shows the overall response category and percentage of patients in each of them. Left column shows the frequency of bleeding and clinically relevant non-major (CRNM) bleeding according to response category. Right column shows the frequency of patterns of response in each response category depending on whether the response was sustained or there were fluctuations over time. n: number.
Older age at the time of diagnosis was reported to be an independent predictor of CR in the previous analysis of this Registry3 and age at the time of diagnosis was highly correlated with age at the time of splenectomy in the present study. Younger age is considered a predictor of CR/R in adult patients with ITP undergoing splenecto- my,11,12 perhaps indicating that there might be a similar underlying mechanism among teenagers and young adults. Older age is also a predictor of chronic ITP in pediatrics,13 further indicating a distinct pathophysiology in ITP affecting teenagers and young adults. It is also pos- sible that patients who undergo splenectomy at a young age are also more refractory to treatment.
Higher platelet counts in the first month post-splenec- tomy was also an independent predictor of both CR/R in this population. Interestingly, higher platelet counts immediately before surgery, not having platelet counts <100x109/L in the first 30 days post-splenectomy, and higher peak platelet count in the first 30 days post- splenectomy were predictors of CR/R in univariable analysis. Ahmed et al. reported that platelet count at the time of splenectomy was one of the predictors of CR/R in a cohort of 254 patients that included 87 children.14 In addition, high platelet count in the first week after splenectomy has been shown to predict response in some studies conducted in adult patients, although results are
inconsistent.10 A more recent study among 174 adults splenectomized for ITP showed that higher pre- and post-operative platelet count were predictors of response in univariable analysis.12 Importantly, pre-surgical and early post-surgical platelet counts may be influenced by platelet enhancing therapy administered pre-operatively in addition to the thrombocytosis seen after splenectomy. Taken together, these observations indicate that individ- uals able to increase and sustain platelet counts in response to an intervention are more likely to show CR/R in the long term.
The present study has some limitations. For example, biases such as selection bias and information bias of an intercontinental registry cannot be ruled out. However, one-third of the patients included in the Registry come from a systematic search at a single center (SickKids) which could help, in part, overcome the issue of selection bias. In addition, the median follow-up time was 25 months, despite the fact that the registry has been open for two decades. Retention can be problematic in reg- istries, particularly when they are voluntary. However, use of registry data can be beneficial as registries are also characterized by strong external validity in view of the heterogeneous populations included, thus better reflect- ing clinical practice.15 In addition, the differential diagno- sis in terms of primary or secondary ITP was left to the
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haematologica | 2020; 105(11)