Pharmacogenetic studies can help investigate the underlying mechanisms of adverse drug reactions and, based on these, develop diagnostic markers to better predict them. Heparin-induced thrombocytopenia (HIT) is the development of thrombocytopenia (low platelet count) following the administration of heparin, an anticoagulant. HIT predisposes to thrombosis and the abnormal formation of blood clots in a vessel. In cooperation with our partner Reinhold Kreutz (Charité-Universitätsmedizin, Berlin), we conducted a GWAS for HIT in 96 individuals affected by HIT following heparin administration and 96 age- and sex-matched individuals without this adverse drug reaction using the 370CNV Infinium bead array. In 2010, a screening experiment identified two genomic loci located on chromosomes 5 and 18 that were significantly associated with the development of HIT with genome-wide significance (p<10-6). Fifteen of the 16 SNPs identified in the screening phase were successfully replicated in an independent sample (96 HIT patients/96 controls). We estimated the effects of these genetic markers in predicting the occurrence of HIT using ensemble classifier unifying support vector machines, random forest, Bayes, and KNN algorithms and found that by including nine independent genetic loci, the prediction accuracy for the occurrence of HIT could be improved to 66.9%. These genetic markers are expected to improve our ability to predict the occurrence of an unwanted drug reaction, thus directly contributing to clinical progress. In 2012, analogous to our approach in the pediatric stroke and thromboembolism projects, we resequenced the chromosome 5 locus in 96 samples with HIT from the original cohort. Enriched DNA libraries were generated and then sequenced using NGS technology at the LIFA's Core Facility for High-Throughput Genetics and Genomics. In 2013, bioinformatics analysis of the NGS data confirmed an insertion on chromosome 5, which is located in close proximity to the associated SNP and is also significantly associated with the occurrence of HIT. These data are currently being prepared for publication together with the results of the initial GWAS and will be submitted shortly.