BACKGROUND Office physicians are unable to measure hair quantity, hair loss, and hair growth in a simple and meaningful manner. One solution is to measure the cross-sectional area of a bundle of hair that is growing within a premeasured cross-section of scalp. OBJECTIVE The objective was to design a mechanical device that precisely measures the cross-sectional area of a bundle of hair and design a device that can precisely delineate an area of scalp. It was assumed that density and diameter changes are evidenced by changes in the bundle cross-sectional area and that growth and loss are the result of density and diameter changes. These assumptions were confirmed using various sized bundles of known diameter non-hair filaments. MATERIALS AND METHODS Bundles of hair and surgical silk fibers were tested using a mechanical device that compressed the bundle and measured its cross-sectional area. Balding patients were categorized according to their observed severity of the loss. Bundles of their uncut hair from 4-cm2 scalp sites were measured and the values were compared to the patient's category of hair loss severity. RESULTS In patients with balding, there was a direct correlation between the bundle's cross-sectional area and the observed severity of the loss. The cross-sectional area was expressed as square millimeters of hair per square centimeter of skin × 100 (mm2/cm2 × 100) and named the trichometric index (TI). Using surgical silk fibers, there was a direct correlation between the bundle's cross-sectional area and the number of filaments, the diameter of the filaments, and the dry weight of the filament bundle. Using aggregates of cut human hair, there was a direct correlation between the cross-sectional area and the dry weight of the bundle. CONCLUSION This prototype device shows promise as a diagnostic instrument for measuring changes in hair quantity (mass), hair diameter, and hair density, as evidenced by preliminary studies using silk sutures, cut human hair, and patients with various degrees of balding. Formal clinical studies are needed. Although the device itself showed a high degree of precision, the accuracy and reproducibility of the measurements can be compromised if the sampling method is not carefully performed using magnification. The device is intended for use on uncut hair that is more than 1 inch in length.
ASJC Scopus subject areas