VVV K_s phase-folded light curves for some variable stars in M 22 in common with the OGLE catalog, as examples of how their quality changes with the ρ parameter defined in the text. From top to bottom: light curves are ordered according to their decreasing ρ value. Upper two panels: with the higher ρ values, represent clear identifications of the variable nature of these stars according to their VVV light curves. The third panel, where ρ = 1.50, represents a detection just in our cutoff point. Lower panel: poor quality of the VVV light curve makes it difficult to separate this true variable source from other false triggers with similar ρ values, rendering their identification as a real variable problematic.