043 The reliability and reproducibility of horizontally sectioned scalp biopsies in the diagnosis of chronic diffuse telogen hair loss in women.

R Sinclair1, D Jolley2, R Mallari3, J Magee4 Dept. of Dermatology, University of Melbourne1, School of Health Sciences, Deakin University, Melbourne Australia2, Dept. of Dermatology, St Luke’s Medical Centre, Manila, Philippines3 Dorovitch pathology, Melbourne4

The diagnostic and predictive value of horizontal sections of scalp biopsy specimens has been studied in male pattern androgenetic alopecia. As women with female pattern balding (FPB) have diffuse hair loss over the crown, a single 4mm horizontal section biopsy may not be accurate. To assess this 207 women presenting with chronic diffuse telogen hair loss were studied prospectively. Three 4mm punch biopsies were taken from immediately adjacent skin in a line on the vertex scalp. The terminal to vellus hair ratio (T:V) at the mid-isthmus level was used to categorize women as: FPB (T:V<4:1), chronic telogen effluvium (CTE) (T:V>8:1) or indeterminate (T:V= 5:1, 6:1 or 7:1). Among 207 women, 159 (77%) were diagnosed with FPB on the basis of consensus over 3 biopsies, 44 (21%) as CTE and the remaining 4 women (2%) were indeterminate. Using each single biopsy as the criterion for diagnosis, there were 621 biopsies from the 207 women. Of these 398 (61%) would be classified as FPB on the basis of T:V alone, 99 (16%) as CTE and 124 (20%) as indeterminate. Overall in 493 (79%) biopsies, the single horizontal biopsy conclusion was identical to the 3 biopsy. Of the remaining 21% of biopsies for which disagreement was seen, most were classified as indeterminate, rather than a wrong diagnosis. Of the 477 ”true” FPB biopsies, only 3.3% were wrongly classified as CTE. To measure the consistency between repeated quantitative measurements on the same subject, the interclass coefficient was determined using a one way analysis of variance (ANOVA), and found to be 0.53 with a 95% confidence interval from 0.45 to 0.60. The within-person standard deviation (SD) was 3.3 which is large given the diagnostic cutpoint for FPB is a T:V of = 4.0. When calculated within diagnostic categories, for FPB the ICC is 0.30 with a SD of 1.66. For CTE the ICC is 0.16 with a SD of 6.6- unacceptable when a cutoff between 4 and 8 is used to distinguish the diagnosis. These results demonstrate that a single 4mm horizontal scalp biopsy is not sufficient for a definitive diagnosis and multiple biopsies are required for accurate diagnostic definition.