Platelet-specific antibodies and differences in their expression in childhood immune thrombocytopenic purpura predicts clinical progression

Machine learning models developed and internally validated for predicting chronicity in pediatric immune thrombocytopenia

BACKGROUND

Primary immune thrombocytopenia (ITP) in children is typically self-limiting; however, 20% to 30% of patients may experience prolonged thrombocytopenia lasting over a year. The challenge is predicting chronicity to ensure personalized treatment approaches.

OBJECTIVES

To address this issue, we developed and internally validated 4 machine learning (ML) models using demographic and immunologic characteristics to predict the likelihood of chronicity.

METHODS

The present study was conducted at Beijing Children's Hospital from June 2018 to December 2021, aiming to develop predictive models for determining the chronicity of pediatric ITP. Four ML models, based on a logistic regression classifier, random forest classifier, eXtreme Gradient Boosting (XGBoost), and support vector machine, were employed. These models used a set of 16 variables, including 14 immunologic and 2 demographic predictors. The performance evaluation criteria included prediction accuracy, precision, recall, F1 score, and area under the receiver operating characteristic curve (AUROC).

RESULTS

Data were collected from 662 patients who were randomly assigned to either a training dataset or a testing dataset using a random number generator. Among them, 26.5% had chronic disease. All models performed well, with AUROC values ranging from 0.81 to 0.84, and XGBoost was selected for its highest AUROC score and interpretability in constructing the predictive model. Age, T helper 17, T helper 17-to-regulatory T cell ratio, T helper 1, and double-negative T cells were identified as significant predictors by the XGBoost algorithm.

CONCLUSION

We developed a precise predictive model for chronicity in pediatric ITP using ML during the initial phase. The XGBoost model achieved high predictive accuracy by using individual patient clinical parameters and demonstrated commendable interpretability.

Efficacy and safety of mycophenolate mofetil in patients with immune thrombocytopenic purpura: a systematic review and meta-analysis

BACKGROUND

Immune thrombocytopenic purpura (ITP) is a challenging disease in its presentation and management as it may cause life-threatening hemorrhaging in vital organs and may resist several lines of treatment. This systematic review and meta-analysis aimed to evaluate the safety and efficacy of mycophenolate mofetil (MMF) in treating patients with ITP.

METHODS

We systematically searched four electronic databases (PubMed, Scopus, Web of Science, and Cochrane Central Register of Controlled Trials) from inception until 10 October 2022. We included all clinical trials, either controlled or single arm, and prospective and retrospective observational studies that evaluate the efficacy and safety of MMF in patients with ITP. We assessed the risk of bias using three tools (ROBINS-I, Cochrane ROB-2, and NIH), each for eligible study design.

RESULTS

Nine studies were included in this meta-analysis, with a total of 411 patients with ITP. We found that MMF demonstrated an overall response rate of (62.09%; 95% CI = [43.29 to 77.84]) and the complete response rate was (46.75%; 95% CI = [24.84 to 69.99]). The overall proportion of adverse events was (12%; 95% CI = [6 to 24]). After the sensitivity analysis, the overall response rate became 50%; 95% CI = [38 to 63]) and the complete response rate became (32%; 95% CI = [24 to 42]). However, MMF did not appear to affect white blood cell counts or hemoglobin levels significantly.

CONCLUSION

This systematic review and meta-analysis demonstrate that MMF appears to be an effective and relatively safe treatment option for patients with ITP when combined with steroids and even in those who have not responded to standard therapies (steroid-resistant cases). Further research with well-designed studies is warranted to better understand the factors influencing treatment response and to refine the use of MMF in the management of ITP. An interactive version of our analysis can be accessed from here: https://databoard.shinyapps.io/mycophenolate_meta/.

Anti-glycoprotein autoantibodies are related to bleeding severity in children with newly diagnosed ITP and very low platelet counts

BACKGROUND AND OBJECTIVE

Immune thrombocytopenia (ITP) is an autoimmune-mediated hemorrhagic disease. Anti-glycoprotein autoantibodies play a key role in the pathophysiology of ITP, but the relationship between platelet-specific antibodies and bleeding severity is unclear. This study aimed to analyze the relationship between anti-glycoprotein autoantibodies and bleeding severity in children with newly diagnosed ITP and platelet count less than 10 × 10⁹ /L.

METHOD

This was a single-center prospective observational study that analyzed children with newly diagnosed ITP and platelet count less than 10 × 10⁹ /L between June 2018 and September 2021 at our hospital. The children were classified into the mild and severe groups based on the bleeding scores. The type and titer of anti-glycoprotein autoantibodies were detected using an enzyme-linked immunosorbent assay (ELISA) kit (PAKAUTO). We analyzed the relationship between bleeding severity and anti-glycoprotein autoantibodies.

RESULTS

A total of 86 cases were enrolled, including 42 in the mild group and 44 in the severe group. Patients with anti-GPIIb/IIIa or anti-GPIb/IX antibodies suffered more severe bleeding than patients without them (χ² = 7.303, p = .007; χ² = 3.875, p = .049), but there was no significant difference between patients with or without anti-GPIa/IIa antibodies (χ² = 0.745, p = .388). When antibodies were analyzed together, patients with three antibodies suffered more severe bleeding than those without three antibodies (χ² = 5.053, p = .025). Patients with higher antibody titer in the eluent, but not in the plasma, suffered more severe bleeding in all three antibodies (Z = -2.389, p = .017; Z = -2.108, p = .035; Z = -2.557, p = .011).

CONCLUSION

Anti-glycoprotein autoantibodies led to more severe bleeding in children under 18 years of age without drug treatment with newly diagnosed ITP and platelet count less than 10 × 10⁹ /L.

An Update on Pediatric Immune Thrombocytopenia (ITP): Differentiating Primary ITP, IPD, and PID

Immune thrombocytopenia (ITP) is the most common acquired thrombocytopenia in children and is caused by both immune-mediated decreased platelet production and increased platelet destruction. In the absence of a diagnostic test, ITP must be differentiated from other thrombocytopenic disorders, including inherited platelet disorders (IPD). In addition, a diagnosis of secondary ITP due to a primary immune deficiency (PID) with immune dysregulation may not be apparent at diagnosis but can alter management and should be considered in an expanding number of clinical scenarios. The diagnostic evaluation of children with thrombocytopenia will vary based on the clinical history and laboratory features. Access to genotyping has broadened the ability to specify the etiology of thrombocytopenia, while increasing access to immunophenotyping, functional immunologic and platelet assays, and biochemical markers has allowed for more in-depth evaluation of patients. With this greater availability of testing, diagnostic algorithms in patients with thrombocytopenia have become complex. In this article, we highlight the diagnostic evaluation of thrombocytopenia in children with a focus on ITP, including consideration of underlying genetic and immune disorders, and utilize hypothetical patient cases to describe disease manifestations and strategies for treatment of pediatric ITP.

Biological stratification of clinical disease courses in childhood immune thrombocytopenia

BACKGROUND

In childhood immune thrombocytopenia (ITP), an autoimmune bleeding disorder, there is a need for better prediction of individual disease courses and treatment outcomes.

OBJECTIVE

To predict the response to intravenous immunoglobulins (IVIg) and ITP disease course using genetic and immune markers.

METHODS

Children aged younger than 7 years with newly diagnosed ITP (N = 147) from the Treatment With or Without IVIG for Kids with ITP study were included, which randomized children to an IVIg or observation group. A total of 46 variables were available: clinical characteristics, targeted genotyping, lymphocyte immune phenotyping, and platelet autoantibodies.

RESULTS

In the treatment arm, 48/80 children (60%) showed a complete response (platelets ≥100 × 109 /L) that lasted for at least 1 month (complete sustained response [CSR]) and 32 exhibited no or a temporary response (absence of a sustained response [ASR]). For a biological risk score, five variables were selected by regularized logistic regression that predicted ASR vs CSR: (1) hemoglobin; (2) platelet count; (3) genetic polymorphisms of Fc-receptor (FcγR) IIc; (4) the presence of immunoglobulin G (IgG) anti-platelet antibodies; and (5) preceding vaccination. The ASR sensitivity was 0.91 (95% confidence interval, 0.80-1.00) and specificity was 0.67 (95% confidence interval, 0.53-0.80). In the 67 patients of the observation arm, this biological score was also associated with recovery during 1 year of follow-up. The addition of the biological score to a predefined clinical score further improved the discrimination of favorable ITP disease courses.

CONCLUSIONS

The prediction of disease courses and IVIg treatment responses in ITP is improved by using both clinical and biological stratification.

Anti-platelet antibody immunoassays in childhood immune thrombocytopenia: a systematic review

BACKGROUND

In adult immune thrombocytopenia (ITP), an acquired autoimmune bleeding disorder, anti-platelet autoantibody testing may be useful as a rule-in test. Childhood ITP has different disease characteristics, and the diagnostic and prognostic value of anti-platelet antibody testing remains uncertain.

OBJECTIVE

To systematically review the diagnostic accuracy of anti-platelet autoantibody testing in childhood ITP.

METHODS

PubMed and EMBASE were searched for studies evaluating immunoassays in childhood ITP. Study quality was assessed (QUADAS2), and evidence was synthesized descriptively.

RESULTS

In total, 40 studies (1606 patients) were identified. Nine studies reported sufficient data to determine diagnostic accuracy measures. Anti-platelet IgG antibody testing showed a moderate sensitivity (0·36-0·80 platelet-associated IgG [direct test]; 0·19-0·39 circulating IgG [indirect test]). In studies that reported control data, including patients with non-immune thrombocytopenia, specificity was very good (0·80-1·00). Glycoprotein-specific immunoassays showed comparable sensitivity (three studies) and predominantly identified IgG anti-GP IIb/IIIa antibodies, with few IgG anti-GP Ib/IX antibodies. Anti-platelet IgM antibodies were identified in a substantial proportion of children (sensitivity 0·62-0·64 for direct and indirect tests).

CONCLUSION

The diagnostic evaluation of IgG and IgM anti-platelet antibodies may be useful as a rule-in test for ITP. In children with insufficient platelets for a direct test, indirect tests may be performed instead. A negative test does not rule out the diagnosis of ITP. Future studies should evaluate the value of anti-platelet antibody tests in thrombocytopenic children with suspected ITP.

Anti-platelet antibodies in childhood immune thrombocytopenia: Prevalence and prognostic implications

BACKGROUND

Anti-platelet antibody testing may be useful for the diagnosis and management of childhood immune thrombocytopenia (ITP).

OBJECTIVES

Here we aimed to assess the prevalence and prognostic significance of anti-platelet glycoprotein-specific IgM and IgG antibodies.

METHODS

Children with newly diagnosed ITP were included at diagnosis and randomized to an intravenous immunoglobulins (IVIg) or careful observation group (TIKI trial). In this well-defined and longitudinally followed cohort (N = 179), anti-platelet glycoprotein-specific IgM and IgG antibodies were determined by monoclonal antibody-immobilization of platelet antigens.

RESULTS

The dominant circulating anti-platelet antibody class in childhood ITP was IgM (62% of patients); but IgG antibodies were also found (10%). Children without IgM platelet antibodies were older and more often female. There was weak evidence for an association between IgM anti-GP IIb/IIIa antibodies and an increased bleeding severity (P = .03). The IgM and IgG anti-platelet responses partially overlapped, and reactivity was frequently directed against multiple glycoproteins. During 1-year follow-up, children with IgM antibodies in the observation group displayed a faster platelet recovery compared to children without, also after adjustment for age and preceding infections (P = 7.1 × 10-5 ). The small group of patients with detectable IgG anti-platelet antibodies exhibited an almost complete response to IVIg treatment (N = 12; P = .02), suggesting that IVIg was particularly efficacious in these children.

CONCLUSIONS

Testing for circulating anti-platelet antibodies may be helpful for the clinical prognostication and the guidance of treatment decisions in newly diagnosed childhood ITP. Our data suggest that the development of even more sensitive tests may further improve the clinical value of antibody testing.