Don't know without more information.
It depends what the athlete's baseline Hct is. If baseline is low 40s then 55 is definitely suspicious. However, a high 40s/low 50s it isn't - a few percentage points increase could be from altitude training, dehydration, etc. There are some athletes who have documented naturally high Hcts in the low 50s who aren't altitude natives.
In 1997 the UCI implemented the 50% upper Hct limit for safety reasons. Some riders were pushing dangerously high Hct levels into the 60s (polycythemia). In fact, some riders like Bjarne Riis even had a nickname for his high crit levels ("Mr. 60 percenter"). However, the upper 50% Hct level has since been replaced by the ABP, which tracts increases in Hct based on the athlete's individual baseline. Too high or consistently suspicious increases can result in a sanction for hematological anomalies.
Nada...none.