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Evidence for Three Distinct Classes of Phenotype Severity in Beta-Thalassaemia
18 Pages Posted: 20 Feb 2019More...
Background: Classification of phenotype severity in patients with beta-thalassaemia has so far relied mainly on expert opinion using parameters of genotype, clinical features at diagnosis, and transfusion requirement. The aim of this study was to use a large dataset of patients with beta-thalassaemia and evaluate a classification system based on onset variables agreed on by an international expert group, including age at diagnosis, at first transfusion, and at first iron chelation.
Methods: A retrospective dataset of 7910 patients with homozygous or compound heterozygous beta-thalassaemia was used and subjected to cluster and classification analysis starting with the onset variables.
Results: Cluster analysis suggested that three clusters with minimal overlapping exist. Three phenotype severity classes (mild, moderate, severe) were accordingly assigned which showed statistically significant descending variation of age at diagnosis and start of transfusion and iron chelation. The estimated classification error rate was only 3.07% with an accuracy of 96.93%. It was evident that severe patients had higher blood requirement and iron overload levels and showed a younger age for mortality especially from heart disease. Although mild and moderate patients showed the opposite in gradual severity, they still showed evidence of high morbidity rate for complications that require longer time to manifest (eg liver damage and hepatocellular carcinoma).
Conclusion: Age of diagnosis and start of transfusion and iron chelation distinguish three classes of phenotype severity in beta-thalassaemia that carry unique clinical profiles. Further prospective studies are recommended to validate these findings.
Funding Statement: The authors state: "None"
Declaration of Interests: The authors state: " None to disclose."
Ethics Approval Statement: An International Health Repository (IHR) protocol, approved on May 25th, 2017 by the Italian Ethical Committee (EudraCT and Sponsor's Protocol Code Numbers were 2017-004457-17 and 143AOR2017) was established to allow collection of relevant data.
Keywords: classification; indexes of phenotype severity; random forest clustering; clinical severity
Suggested Citation: Suggested Citation