RESUMO
Introduction: Precise evaluation of changes in hair count is crucial for monitoring progression of hair loss and the effects of treatment. The focus of this study is the comparison of the various examination and assessment techniques in terms of the precision of hair count change observed in trichoscopy images. Methods: Controlled hair extraction of the same scalp spot was used to simulate hair loss, and the different examination techniques were performed to detect this change. The investigators who performed the counting were blinded. Results: For trichoscopy images, the average error in determining the terminal hair count change (relative to total hair count) was 9 ± 1% for automatic assessment with manual correction and 0.4 ± 0.2% for hair-to-hair matched images. For phototrichogram, the automatic measurement results were found to deviate from truth on average by 12 ± 2%. The manually corrected hair count results were much closer to the truth with average deviation at the level of 7 ± 1%. The hair-to-hair matched results corresponded to approximately 0.6 ± 0.3% average discrepancy. Conclusion: Combination of manually corrected image processing, follicular mapping, and hair-to-hair matching appears to be the most precise way of evaluating the change in hair count over time. These novel techniques should be considered valuable, especially in research and clinical trials.