Morphometry in skin-test methodological studies--validation of the point-counting technique for precise area...

The methods for delimiting and measuring cutaneous responses can significantly influence the result of skin tests. For this reason, when skin tests are used for purposes of clinical research, the use of computerized methods is recommended to reduce the measurement error of traditional methods. In the present study we evaluated the degree of precision and accuracy of the point counting technique, employed in morphometry for measuring plane images.

The degree of precision and accuracy of the point counting technique were studied using a panel of geometric figures (circles and ellipses) of scalar size and some series of wheals and flares of various sizes, from very small dimensions to greater and irregularly-shaped ones, which can represent the different degrees of intensity of cutaneous responses. The efficiency of the method was compared with the efficiency of the traditional one based on the measurement of diameters.

Under the various experimental conditions the average measurement error by the point counting technique was contained within the limit of 8%, with a variation coefficient of about 7%. Unlike the traditional method based on the length of diameters, the point counting technique proves to be very precise and accurate to estimate both areas of small dimensions and very large and irregularly-shaped ones.

The point counting method proved to be reliable and to possess a satisfactory degree of accuracy and precision in the measurement of cutaneous responses of any type. When computerized programmes are not available, the point counting technique can advantageously be used for purposes of clinical research and for methodological studies on prick test procedures.