Contrast enhanced phototrichogram (CE-PTG): an improved non-invasive technique for measurement of scalp hair dynamics in androgenetic alopecia--validation study with histology after transverse sectioning of scalp biopsies.

Global changes of scalp hair represent the cumulative end result of discrete changes of individual hair follicle structure and/or function. Monitoring of such changes requires an accurate non-invasive method. The phototrichogram (PTG) appears to be an appropriate choice to do so. However, a known weakness of the method is the lack of detection of less pigmented or thinning hair. Balding scalp of male subjects with androgenetic alopecia (AGA) was analysed with our previously published PTG method and with contrast enhanced (CE-)PTG followed by biopsy and transverse section examination with the light microscope. As compared with PTG, the CE-PTG method significantly improved detection not only of thin but also of thick hair. Equal numbers of thick (diameter > 40 mm) hair were detected with CE-PTG and with histology. CE-PTG was also able to detect the severely miniaturised hair fiber (down to 8 mm diameter) and was comparable to scalp biopsy analysis. The latter could identify hair fibres, which did not reach the scalp surface, a measure that is considered as not clinically significant. All growth stages - anagen, catagen and telogen - as well as the empty follicle stage could clearly be observed with CE-PTG. Staging of the more severely affected hair follicles was not always possible neither with CE-PTG nor histology - even with serial sectioning. The finding of such technological advantages makes the CE-PTG a first choice method for detailed analysis of hair cycling in androgenetic alopecia - a scalp disorder characterised by extreme hair follicle miniaturisation, decreased hair pigmentation and hair thinning.