Results of research by Al Hadithy A.F. et al. (2008) showed that the carriage of the 141C Del allele of the DRD2 gene encoding D2 receptors is associated with a 9.5-fold greater risk of developing AIP in patients receiving AP in comparison with non-carriers (p = 0.005). This evidence concerns the gene DRD2 and alkaline phosphatase measurement.