title: Setting reference values in trichology.
abstract: BACKGROUND
  In clinical trichology, reference values are often arbitrary. The difficulty in setting them up depends mostly on the presence of the androgenetic alopecia (AGA) genotype in subjects with clinically unapparent forms. Prepubertal children, who lack 5α-reductase (a real indicator of the AGA phenotype), might provide reference values independent from AGA. We verified whether the vertex/occiput ratios (V/O) of hair density and the V/O of hair diameter are suitable parameters.
  
  
  METHODS
  In sixty 4-10-year-old Caucasian children, we measured the ratio between the hair density at the vertex and the occiput. The same was done for the diameter.
  
  
  RESULTS
  The V/O of density averaged 1.07 ± 0.17 and the V/O of diameter 1.02 ± 0.11.
  
  
  CONCLUSIONS
  Taking the mean ± 2SD as normal values, our "normal" V/O of density ranged between 0.73 and 1.41 and our "normal" V/0 of diameter between 0.8 and 1.24. People with lower ratios would have, therefore, AGA with 95% of probability. Moreover, we found that hair shedding using the hair pull test and the modified wash test come to 1-2 hairs/day.
authors.affiliation: DISSAL, Section of Dermatology, IRCCS Azienda Universitaria Ospedaliera San Martino-IST, Genoa, Italy.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Rebora
authors.affiliation: DISSAL, Section of Dermatology, IRCCS Azienda Universitaria Ospedaliera San Martino-IST, Genoa, Italy.
authors.forename: Marcella
authors.initials: M
authors.lastname: Guarrera
authors.affiliation: DISSAL, Section of Dermatology, IRCCS Azienda Universitaria Ospedaliera San Martino-IST, Genoa, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Drago
authors.affiliation: Department of Internal Medicine and Medical Specialties, University La Sapienza, Rome, Italy.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Rossi
authors.affiliation: Department of Internal Medicine and Medical Specialties, University La Sapienza, Rome, Italy.
authors.forename: Maria Caterina
authors.initials: MC
authors.lastname: Fortuna
authors.affiliation: S.Camillo Hospital, Monopoli (Bari), Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: D'Ovidio
authors.affiliation: S.Camillo Hospital, Monopoli (Bari), Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Chieco
authors.affiliation: Department of Experimental, Diagnostic and Specialty Medicine, Division of Dermatology, University of Bologna, Bologna, Italy.
authors.forename: Bianca Maria
authors.initials: BM
authors.lastname: Piraccini
authors.affiliation: Department of Experimental, Diagnostic and Specialty Medicine, Division of Dermatology, University of Bologna, Bologna, Italy.
authors.forename: Michela
authors.initials: M
authors.lastname: Starace
mesh_terms: D000505:Alopecia / Q000175:diagnosis* / Q000209:etiology; D002648:Child; D002675:Child, Preschool; D005260:Female; D006197:Hair / Q000033:anatomy & histology; D018859:Hair Follicle / Q000033:anatomy & histology*; D006801:Humans; D008297:Male; D012016:Reference Values; D012494:Sampling Studies; D012535:Scalp; D044465:White People