HTR4 and chronic obstructive pulmonary disease: Association with COPD risk for HHIP and HTR4 had already been reported [15, 18], but not for SPATA9 or MECOM. These four variants were also analysed in UK BiLEVE, where again the association of HHIP and HTR4 were confirmed, but no association was found for SPATA9 or MECOM (Table 1).