Diagnostic Performance of the Trichogram Compared to Histopathology of Scalp Biopsy in Horizontal Sections in Female Androgenetic Alopecia: A Retrospective Study.

Abstract

Introduction: Female androgenetic alopecia (FAGA) is a frequent cause of diffuse, non-scarring hair loss in women. The trichogram is a noninvasive method for assessing follicular miniaturization, but its diagnostic accuracy compared with scalp biopsy remains uncertain.

Methods: In this retrospective, cross-sectional study, 49 women with suspected FAGA underwent trichogram and scalp biopsy on the same day. Hair shafts were classified using three approaches: (1) standard classification (terminal >0.03 mm; vellus ≤0.03 mm or thinner than the inner root sheath, per Headington's criteria); (2) T:(V+I) classification (terminal >0.06 mm, intermediate >0.03-0.06 mm, vellus ≤0.03 mm); and (3) relative diameter method, where hairs <50% of the thickest shaft were considered vellus. In all methods, a terminal-to-vellus ratio ≤3 indicated diagnosis.

Results: Standard classification yielded a sensitivity of 65.3%. When intermediate and miniaturized hairs were combined, sensitivity increased to 96%. The relative diameter method achieved 77.6%, with no significant difference from histopathology.

Conclusion: Trichogram sensitivity in FAGA improves when intermediate hairs are included or when relative shaft diameter is applied. These adaptations enhance correlation with histology and support the trichogram as a practical, noninvasive, and cost-effective diagnostic tool in clinical practice.