A comparative study of the accuracy of area assessment by point counting for bronchial mucous glands

The accuracy with which areas of bronchial mucous gland on histological sections may be determined has been investigated with respect to inherent statistical variability in the point counting procedure used, and with respect to variations between the histological stains and observers employed. Very good argeement was obtained between areas determined by point counting and by planimetry. It was shown empirically that for sections of well-defined gland-like structures the accuracy (coefficient of area) of area determination was inversely proportional to the 3/4 power of the mean point count. The constant of proportionality depended on the structure's shape and on the point geometry of the grid used. Using the relationship the count needed to achieve a required accuracy of area determination could be established. It was shown that in general a smaller count was required for a given accuracy than would be the case using randomly dispersed tissue. On histological sections the accuracy of area determination is also dependent upon gland boundary definition, and our experiments showed that a recticulin Alcian Blue stain best defined mucous gland acini, and that a PBS stain gave the most accurate results for whole gland. These experiments also showed that there were small but significant differences in mean areas determined by different observers. The observers were shown to be equally consistent in their judgment of what constituted whole mucous gland and acini, but since they differed over mean counts it is recommended that studies should be designed to use either a single observer or to assign observers randomly among groups. With these considerations point counting can be made an accurate method of area determination for these or similar tissues.