Idiopathic autoimmune thrombocytopenia and neutropenia in siblings

Immune thrombocytopenia in adults: a prospective cohort study of clinical features and predictors of outcome

This prospective observational cohort study aimed to explore the clinical features of incident immune thrombocytopenia in adults and predictors of outcome, while determining if a family history of autoimmune disorder is a risk factor for immune thrombocytopenia. All adults, 18 years of age or older, recently diagnosed with immune thrombocytopenia were consecutively recruited across 21 hospital centers in France. Data were collected at diagnosis and after 12 months. Predictors of chronicity at 12 months were explored using logistic regression models. The association between family history of autoimmune disorder and the risk of developing immune thrombocytopenia was explored using a conditional logistic regression model after matching each case to 10 controls. One hundred and forty-three patients were included: 63% female, mean age 48 years old (Standard Deviation=19), and 84% presented with bleeding symptoms. Median platelet count was 10×10(9)/L. Initial treatment was required in 82% of patients. After 12 months, only 37% of patients not subject to disease-modifying interventions achieved cure. The sole possible predictor of chronicity at 12 months was a higher platelet count at baseline [Odds Ratio 1.03; 95%CI: 1.00, 1.06]. No association was found between outcome and any of the following features: age, sex, presence of either bleeding symptoms or antinuclear antibodies at diagnosis. Likewise, family history of autoimmune disorder was not associated with incident immune thrombocytopenia. Immune thrombocytopenia in adults has been shown to progress to a chronic form in the majority of patients. A lower platelet count could be indicative of a more favorable outcome.

A case-control study to assess the risk of immune thrombocytopenia associated with vaccines

The cause of immune thrombocytopenia (ITP) remains unknown. Studies have suggested immunizations as possible triggering factors of ITP through molecular mimicry. This case-control study explored potential associations between adult ITP and various routinely administered vaccines. A network of internal medicine and hematology centers across France recruited 198 incident (ie, newly diagnosed) cases of ITP between April 2008 and June 2011. These cases were compared with 878 age- and sex-matched controls without ITP recruited in general practice. Information on vaccination was obtained from patients' standardized telephone interviews. Sixty-six of 198 cases (33.3%) and 303 of 878 controls (34.5%) received at least 1 vaccine within the 12 months before the index date. We found no evidence of an increase in ITP after vaccination in the previous 6 or 12 months (adjusted odds ratio [OR] for the previous 12 months = 1.0; 95% confidence interval, 0.7-1.4). When the 2-month time window was used, higher ORs were observed for all vaccines (OR = 1.3). This increase was mainly attributable to the vaccination against diphtheria-tetanus-pertussis-poliomyelitis (OR = 1.5) and was not statistically significant. The results of the present study show that in an adult population, the exposure to common vaccines is on average not associated with an observable risk of developing ITP.

Unappreciated HLA Antibodies in Adult Immune Thrombocytopenic Purpura

BACKGROUND/PURPOSE

Immune thrombocytopenic purpura (ITP) is an autoimmune disease. Platelet refractoriness is frequently seen in patients with ITP. Platelets express platelet-specific antigens and human leukocyte antigens (HLA). Platelet antibodies to platelet-specific antigens and HLA may be present, but HLA antibodies in patients with ITP have rarely been reported.

METHODS

Sera from 44 adult patients with ITP were screened for platelet antibodies by two flow cytometric assays. In method I, platelets from normal donor platelets were used as target cells to screen both platelet-specific antibodies and HLA class I antibodies. In method II, the FlowPRA Class I Screening Test kit was used to screen HLA class I antibodies. Fluorescein isothiocyanate (FITC)-conjugated sheep anti-human IgG Fc was used as the staining reagent in both methods. The negative serum control was from one of the normal males with AB blood group who had never received a transfusion. Sera from a pool of five highly sensitized patients were used as the positive control.

RESULTS

Of the 44 sera from patients with ITP, 31 (70.5%) were method I positive, and 28 (63.6%) were method II positive. There was no significant difference between the results of method I and method II (p = 0.439). The distribution of the results of these two tests was: both tests positive in 22 sera, method I positive and method II negative in nine sera, method I negative and method II positive in six sera, and both tests negative in seven sera. The mean platelet counts of patients with positive (41.0 +/- 40.0 x 10(9)/L) and negative (40.4 +/- 26.8 x 10(9)/L) tests by method I did not differ significantly (p = 0.643). The mean platelet counts of patients with (36.7 +/- 31.5 x 10(9)/L) and without (48.1 +/- 43.6 x 10(9)/L) HLA class I antibodies did not differ significantly (p = 0.59).

CONCLUSION

HLA class I antibodies are frequently found in ITP. The screening of platelet antibodies including platelet-specific antibodies and unappreciated HLA class I antibodies is warranted in patients with ITP.

Screening for platelet antibodies in adult idiopathic thrombocytopenic purpura: a comparative study using solid phase red cell adherence assay and flow cytometry

BACKGROUND

Idiopathic thrombocytopenic purpura (ITP) is an autoimmune disorder caused by antiplatelet autoantibodies. In this study, we compared 2 methods for screening serum platelet antibodies in patients with ITP.

METHODS

A total of 44 adult patients were clinically classified with ITP. We used 2 indirect tests to detect human leukocyte antigen antibodies and/or platelet-specific antibodies in their sera. In method I, we used solid phase red cell adherence (SPRCA) assay. In method II, by flow cytometry, platelets from plateletpheresis components were used as target cells, and fluorescein isothiocyanate-conjugated sheep anti-human IgG Fc was used as the staining reagent. Positive results were defined as any test with the percentage of fluorescence exceeding the reference range by 3% or more in method II. Direct tests detecting platelet-associated IgG on platelets of patients with ITP were done by flow cytometry.

RESULTS

Serum specimens from 44 adult patients with ITP (28 female, 16 male) were tested. SPRCA assay could only detect platelet antibodies in 22 patients (50%). By method II, 31 serum specimens (70.5%) yielded positive results. There was a difference between the results of the SPRCA test and method II, with a high degree of significance (p < 0.001) by the McNemar test. No significant difference in platelet counts was observed for patients with and without discernible platelet antibodies by SPRCA assay (p = 0.90). The direct test was positive in 12 patients (66.7%) out of 18 ITP patients tested.

CONCLUSION

Flow cytometry is more sensitive than SPRCA assay for detecting platelet antibodies. Detection of platelet antibodies is useful in explaining the immune mechanism and platelet transfusion refractoriness in ITP.

Idiopathic thrombocytopenic purpura (ITP): is there a genetic predisposition?

Idiopathic thrombocytopenic purpura (ITP) is a diagnosis of exclusion. It is unknown, whether familial ITP exists. Familial cases would make a genetic susceptibility for ITP possible. Data of the Pediatric and Adult Registry on Chronic ITP (PARC-ITP) were reviewed and subsequently ITP patients from Basel investigated for cases with a positive family history. In 10 of 445 pediatric patients and in 2 of 21 patients from Basel the family history was positive. A surprisingly high number of ITP patients with a positive family history were identified, indicating the likely existence of a genetic susceptibility for ITP.