GSTM1 and acquired polycythemia vera: As another example, due to long-term residence in Tibet at extremely high altitudes (>4,000 m), the [Hb] of some Tibetans was higher than the main diagnostic criteria for polycythemia vera (PV) (men > 185 g/L, women > 165 g/L) or even higher than that for high-altitude polycythemia (HAPC) (men > 210 g/L, women > 190 g/L) (10).