Abstract
Predictive biomarkers are needed in immune thrombocytopenia (ITP). Single nucleotide polymorphisms (SNPs) in beta 1 tubulin are potential candidates, as beta 1 tubulin is integral for platelet production and function, and SNPs in beta 1 tubulin have been associated with distinct phenotypes in platelets. We investigated the most prevalent beta 1 tubulin SNP (R307H) as a biomarker in patients with ITP via a retrospective chart review. Allelic frequencies between a group of 191 ITP patients and a healthy control group showed no difference, suggesting no direct aetiological role for the SNP in ITP. However, over similar periods of follow-up, both heterozygote and homozygote minor allele ITP patients were treated with significantly more treatment modalities and had significantly higher risk of failure to immune-modulatory therapies [relative risk (RR) = 1·5, 95% confidence interval (CI) = 1·1-2·1; P = 0·01]; with rituximab, in particular, ITP patients with the SNP experienced a 58% failure rate (RR = 1·6, 95%CI = 1·03-2·5; P = 0·04). Analysis of the absolute immature platelet fraction (A-IPF) as a marker of platelet production showed that SNP patients had significantly higher median A-IPFs compared to non-SNP patients when complete responses were achieved using immune modulatory therapies. The data suggest that the beta 1 tubulin R307H SNP has potential for use as a biomarker in ITP and may affect platelet turnover.