Diagnostic value of horizontal versus vertical sections for scarring and non-scarring alopecia: a systematic review and meta-analysis

Histopathological diagnosis of scalp biopsies remains a challenging area in dermatopathology. Published studies have described the benefits of different sectioning techniques although the application of these techniques is still under clinical investigation. To review published literature and evaluate the value of horizontal sections compared to vertical sections in the diagnosis of alopecia. Databases, such as PubMed and EMBASE, among others, were searched for published articles; to identify additional relevant studies, the literature search was performed manually. The total number of cases and diagnosed cases, and diagnostic rates, were extracted from each included study. Pooled diagnostic rates with 95% confidence intervals (CI) were used to evaluate the value of different sectioning techniques, and we tested for publication bias and heterogeneity. Most studies had a suboptimal design. With regards to non-scarring alopecia, there were eight horizontal and eight vertical section studies. The pooled diagnostic rates were 0.81 (95% CI: 0.70-0.92) and 0.76 (95% CI: 0.60-0.93), respectively, and extensive heterogeneity existed among these studies. For the diagnosis of scarring alopecia, there were three horizontal and five vertical sectioning studies. The pooled diagnostic rates were 0.86 (95% CI: 0.66-1) and 0.90 (95% CI: 0.82-0.98), respectively, and heterogeneity was also observed. Based on published studies, no significant difference exists between horizontal and vertical sectioning techniques in the diagnosis of alopecia. Whereas most studies had a suboptimal design, future studies in this area would benefit from a scientific approach and standardised measurements to explore the value of horizontal and vertical sectioning.