To examine whether periodontal disease progression can be accurately determined by Hb examination, healthy sites (PD ≤ 4 mm, BOP (−)) and diseased sites (PD ≥ 4 mm, BOP (+)) in the same oral cavity of SPT patients were reclassified into four groups using the Hb cutoff value. This evidence concerns the gene GSTM1 and periodontal disorder.