GSTM1 and hemoglobinopathy: As with most NBS programs across the world, heterozygous carrier status for hemoglobinopathy mutations is not a target of screening in Ontario, but is identified incidentally; approximately 1% of the 140,000 newborns who receive NBS each year in Ontario are identified as carriers of HbS, HbC, Hb D, or Hb E. These carrier results are made available only to those families who formally request this information through their family physician or directly from Newborn Screening Ontario; i.e., the carrier results are not otherwise disclosed proactively.