A method of evaluating the integrity of a substrate used in medical device packaging include providing a flexible, porous substrate having a first major surface, and a second major surface, applying a UV absorbent layer over at least one of the first and second major surfaces of the substrate, and placing the substrate over a UV reflective surface. The method includes directing UV light toward the substrate and the UV reflective surface, whereby the UV absorbent layer absorbs light in a spectrum that matches the wavelength of the UV light, and detecting with a UV sensitive camera any UV light that is reflected from the first and second surfaces of the substrate. The substrate is rejected if the reflected UV light that is detected by the UV sensitive camera indicates that the substrate has at least one opening having a size that is greater than or equal to 10 microns. The substrate is accepted if the reflected UV light detected by the camera indicates that the substrate has no openings that are greater than or equal to 10 microns.