Hair diameter measurement methods: micrometer caliper versus phototrichogram

Background Hair diameter is a crucial element in deciding the treatment and predicting the prognosis of hair transplantation in patients with hair loss.Methods Ten female volunteers participated in this study. Three sites at different horizontal positions of the scalp were chosen for measurement: midoccipital, mastoid, and temporal. Three boxes of 1 cm2 were marked from superior to inferior along the midline of each site, and five anagen hairs ≥10 cm long were randomly sampled from each box. The thickness of each collected hair was measured at three positions along the hair length: 1 cm, 5 cm, and 10 cm from the surface of the skin. The diameters of the hairs were measured using a micrometer caliper and a Folliscope phototrichogram, and the measurements were compared.Results The average thickness of all hairs was 76.90±12.29 μm when measured with the caliper and 108.78±19.97 μm when measured with the phototrichogram. There was a statistically significant difference between the two measurement methods (P<0.001). The average hair thickness from the three areas (midoccipital, mastoid, and temporal) showed a significant difference between the caliper and the Folliscope hair measurements (P<0.001): midoccipital area (caliper, 74.46±9.71 μm; Folliscope, 109.03±19.59 μm), mastoid area (caliper, 76.36±10.67 μm; Folliscope, 103.73±18.67 μm), and temporal area (caliper, 79.89±15.18 μm; Folliscope, 113.59±20.43 μm).Conclusions Measuring hair thickness using a phototrichogram, which generates a measurement of the long-axis dimension, is clinically useful in the treatment of patients with hair loss and patients undergoing hair transplantation.