Filtering Gaps
While gaps can offer excellent trading opportunities, it’s often difficult to know (except in hindsight) if one is a runaway gap or an exhaustion gap, or some other kind of gap. One of the best filters for determining whether a gap will lead to a short-term runaway move is the ADX. If the ADX reading is high, it means the market is trending. If the market gaps in the direction of its current trend, it means demand is strong. The likelihood of follow-through in the direction of the gap is greater in these situations.
–Larry Connors, Professional Traders Journal