Genetic predictions of eye and hair colour in the Danish population

Genetic predictions of eye and hair colour are prominent examples of forensic DNA phenotyping that can help resolve criminal cases. The advent of high-throughput genotyping technologies in forensic genetics opens up the possibility of applying polygenic risk scores in forensic settings. In this work, we compare the performance of HIrisPlex with PRSice-2 in predicting eye and hair colour to gain insights into the relative benefits of new approaches. Predictions were carried out on 584 Danish high school students for which genetic and self-reported phenotype data were available. Prediction of brown eye colour was very accurate (AUC = 0.98), followed by blue eye colour (AUC = 0.82), while it failed for intermediate eye colour (AUC = 0.57). As for hair colour, red and black were overall better predicted than blond and brown, and PRSice-2 performed better in all but the black hair colour. Despite the limitations of the study, HIrisPlex exhibited its usual high performance in the prediction of brown and blue eye colour, as well as red and black hair colour. However, PRSice-2 offered overall improvements in hair colour prediction over HIrisPlex suggesting that there is room for improvement in forensic DNA phenotyping by using polygenic risk scores.