Inter-Operator Analysis Variability Expressed as Absolute Percent Difference.

When comparing total tube length results as analyzed between operators 1 and 2, a large amount of variability was observed between the two analyses. The relative percent difference between operators was calculated by dividing the absolute difference in quantitation of a single image with the value obtained by the operator that quantified the image a lower total tube length (Equation 1.1). The largest relative percent differences in quantification between operators occurred in images with poorly formed tubes which explains the increased concordance between operators as images with a lower total quantified length were removed (images where either operator quantified the total tube length within an image less than 10,000 μm or 15,000 μm).