In the recent article by de Lacharrière et al,1 the severity of androgenetic alopecia (AGA) as evaluated by means of the Hamilton scale was found to be significantly correlated with the clinical and histological hair density classification. In our experience, this is not the case when hair density and thickness are clinically evaluated.
In a first study,2 two 1-cm2 areas were identified on the vertex and just below the occipital protuberance of 109 men with different degrees of baldness severity. In both areas, hairs were clipped short, photographed by a videomicroscope at ×20 magnification, and counted within a 30-mm2 wide central-square section. On the occipital area, the average count was 127/cm2, without differences among the Hamilton-Norwood classes. On the parietal area, the average density significantly diminished with the increasing AGA severity from 138/cm2 to 47/cm2. As AGA does not affect the occipital area, the parietal-occipital ratio could be considered a good measure of AGA severity. The parietal-occipital ratio, however, decreased significantly from Hamilton classes I to III vertex to Hamilton IV to VI, only when baldness was clinically manifest.
Guarrera M, Vecchio F, Rebora A. Do Hair Density and Thickness Correlate With the Hamilton Scale?. Arch Dermatol. 2002;138(8):1099. doi:10.1001/archderm.138.8.1098