## 3 Measurements to Determine Hair Loss  
How can this hair loss be measured with objective and valid test methods? The hair pulling test, the trichogram, and the dermatoscopy with fully automated hair analysis software are the diagnostic possibilities to objectively confirm subjective hair loss. The hair pulling test is the fastest and simplest type of examination. To do this, a strand of about 60 hairs is wrapped around the thumb and forefinger and gently pulled upwards. If more than 10% of the hair is pulled out without effort and pain, this is considered an indication of a problem [24]. The disadvantage of this test is inaccuracy. Both the exact number of hairs and the force with which they are pulled cannot be standardized. The trichogram is an analysis of the hair roots. Using a clamp, which is covered with a silicone tube to protect the hair, a narrow row of 50-100 hairs is extracted in the direction of growth at two different points. The hair sample is then fixed between two glass plates, and the root area is examined under the light microscope to assign them to the different growth phases. This way, the hairs in the anagen phase can be distinguished from hairs in the telogen phase. Disadvantages of this method are the somewhat painful pulling out of the hair and an incorrect removal technique resulting in the hair breaking off. Furthermore, this method requires a lot of experience to assess the hair root. Furthermore, there are three commercially available devices that combine dermatoscopy with fully automated hair analysis software. These devices are the TrichoScan(r) (FotoFinder Systems GmbH, Bad Birnach, Germany), the FolliscopeTM (LeedM Corporation Seoul, South Korea), and Hair Metrix(r) (Canfield Scientific, Parsippany, NJ, USA) with a simple and fast image processing and image editing. These devices consist of a handheld unit for reflected light microscopy, which captures the scalp under magnification, and corresponding software for hair analysis. In addition, these devices can also be used to assess the scalp for inflammation, dandruff, infection, and scarring and to detect damage to the hair shaft and hair structure as well as hair breakage. The Canfield's HairMetrix(r) offers a fully automatic real-time analysis of the data recorded by the VisioMed D200 evo camera. Both the FolliscopeTM and the Canfield's HairMetrix(r) offer the following parameters: number and size of follicular units, follicular width to see increase/decrease in shaft diameter, measurement of vellus/terminal hair ratio. In principle, however, a manual evaluation of the images regarding anagen and telogen rate would also be possible here with the Folliscope as well as Canfield's HairMetrix(r). TrichoScan(r) is a fully automated method for the measurement of biological parameters of hair growth and hair cycle. The TrichoScan(r) method [25; 26; 27; 28; 29] is a modification of the classic trichogram. Thus, the anagen and telogen hairs are primarily determined as in the trichogram. The TrichoScan(r) software (TrichoScan 3.0 Research Edition, GCP validated), however, is based on the assumption that anagen hair grows by approximately 0.3 mm a day, while telogen hair does not grow [30]. Furthermore, the software can calculate a number of other parameters such as hair density (n/cm\({}^{2}\)), hair diameter (um), hair growth rate (mm/day) and vellus and terminal hair density. The measuring procedure is as follows: On the first day, the test field is identified, and the hair is clipped evenly to a length of 1 mm in a measuring field of 18 mm by means of a mini hair trimmer. Images are taken at a 20-fold magnification in order to evaluate the evenness of the clipped measurement area. After three days, hair growth is monitored after hair dying for approximately 10-15 min. Three images of the same area should be recorded and then analysed by the software [31]. A further development of the computer-aided TrichoScan(r) hair analysis was the FotoFinder TrichoScale(r) system in 2012.