An interesting observation is that using lower f-Hb thresholds to give equivalent positivity for women as for men would have had the largest effect on the proportion of cancers detected by screening in the youngest age quintile, where the ICP would have potentially fallen from 37.1% to 28.6%, despite this group having the lowest decrease in stratified f-Hb threshold. The gene discussed is GSTM1; the disease is cancer.