Mapping the hair density, thickness, and volume in normal and androgenetic alopecia subjects with the digital microscope

Abstract Background Scalp hair density and hair diameters were the two key parameters to the diagnosis of hair loss diseases, including androgenetic alopecia (AGA). Objectives To comprehensively map the hair density and the ratio of terminal‐to‐vellus hair numbers (T/V ratio) on different scalp sites in subjects of different genders, ages, body mass index, and stages of AGA. The impact of the two parameters on visual perception of the hair volume was evaluated. Methods Normal and AGA subjects of both genders were included. Trichosopic pictures were taken by a hand‐held digital microscope at the 11 designed anatomical sites on the scalp and the hair density and T/V ratio were measured based on the pictures. The T/V ratio was defined as the ratio of non‐vellus (terminal or intermediate) hair count to vellus hair count. Results In subjects with normal scalp (n = 49), the hair density and T/V ratio were highest at the parietal and vertex sites in men and women, respectively. In AGA subjects (n = 111), the hair density was significantly decreased at the frontal, parietal and vertex sites in both genders. The hair density at the occipital sites was not significantly changed in alopecia subjects of both genders, but in female alopecia subjects the occipital hair density showed a steadily decreasing trend as the AGA severity increased. The perception of hair volume was impacted more greatly by the T/V ratio than the hair number density. Conclusion The hand‐held digital microscope (videodermoscope) was an easily accessible and noninvasive tool to evaluate hair parameters, in which hair diameters better determined the visual perception of alopecia in AGA.