The use of a digitizer to measure area in dermatology

The accuracy and reproducibility of area measurements made with a computerized digitizer were studied. Known areas were measured varying the way in which the system was operated, altering the characteristics of the shapes being measured and varying the ways in which the image on the computer screen was formed. Accuracy and reproducibility were dependent on all these factors; altering the operating technique caused the mean measured area to vary from 76% to 124% of the actual area, with the greatest inaccuracies being produced by altering the computer screen image. The accuracy and reproducibility of results obtained using a digitizer are critically dependent on the way in which it is used.