Trichoscopic features of androgenetic alopecia according to the basic and specific (BASP) classification: A retrospective observational study
Jeewoo Choi, Mina Song, Sohyun Ahn, Ji Yeon ByunBackground
Androgenetic alopecia (AGA) is a common form of hair loss, where early diagnosis is challenging. Trichoscopy offers a non-invasive method for evaluating androgenetic alopecia, but its relationship with disease severity is not well-established.
Aim
To evaluate the correlation between qualitative and quantitative trichoscopic features and disease severity of androgenetic alopecia graded by the basic and specific (BASP) classification.
Methods
This retrospective study analysed 471 trichoscopic images from 157 Korean participants (129 males, 28 females; 99 with androgenetic alopecia, 58 controls). Disease severity was graded using the BASP classification. Qualitative scalp signs (vellus hair, peripilar sign, yellow dot, pinpoint white dot, focal atrichia, honeycomb pigmentation) and quantitative trichoscopic factors (total hair count, follicular unit composition and follicular unit density) were compared between groups and assessed for trends across BASP stages.
Results
The prevalence of all trichoscopic scalp signs was significantly higher in the androgenetic alopecia group than in controls (e.g., vellus hair, 80.1% vs. 24.2% in occipital controls; p < 0.001). As BASP stages advanced, there was a significant increase in all scalp signs (e.g.,vellus hair prevalence, from 46.9% in BASP 0 to 100% in BASP 3) and the proportion of single-hair follicular units (1FU%, 39.1% to 76.6%). Conversely, total hair count and proportion of multi-hair follicular units decreased significantly with increasing severity (p< 0.001 for trend). Follicular unit density remained stable until the most advanced stage. Additionally, females showed a significantly higher 1FU% than males in the early stage.
Limitations
Retrospective, single-centre design and lack of hair shaft diameter measurement.
Conclusion
A significant association was observed between trichoscopic features and the severity of AGA as graded by the BASP classification. Vellus hairs can serve as an early indicator, and changes in the composition of follicular units, particularly an increased proportion of 1FU%, may serve as quantitative markers of follicular miniaturisation. These findings support the use of trichoscopy as an objective tool for the early detection and monitoring of AGA.