title: Distribution analysis of vitamin D highlights differences in population subgroups: preliminary observations from a pilot study in UK adults.
abstract: There is no consensus between Authors on the definition of a replete or deficient vitamin D state. Our aim was to describe a suitable method that could be used to compare vitamin D data in subject groups with small or large numbers. Two hundred and forty indigenous asymptomatic, non-pregnant adult subjects recruited from a single-consultation outpatient attendance with normal biochemistry, represented a sample of our inner city district population. 25-hydroxyvitamin D (25,OHD3) levels were measured to illustrate the effects of season, sex and ethnic group on vitamin D levels and subjected to distribution analysis. This method quantifies as a percentage the distribution of 25,OHD3 concentrations (observed concentration, OC) in pooled group data. The data can be expressed as distribution frequency domains or cumulative frequency ogives (0-100%) or transformed into discrete linear probits, amenable to regression analysis. An estimate of the OC50 (mid-point) and upper (either OC75 or OC95) or lower (either OC25 or OC5) range or at any other frequency between subject groups can be compared. A marked difference in 25,OHD3 levels between Asian and non-Asian asymptomatic adult subjects was seen during both seasons. 25,OHD3 deficiency was defined as at or below the OC25 for the non-Asian group (for both sexes: winter < 13.36 ng/ml, summer <13.38 ng/ml). The majority of Asians of both sexes were 25,OHD3 deficient (winter 94%, summer 82%). The distribution analysis provides an easy technique to compare 25,OHD3 status of different subject groups, allowing the description of populations using either longitudinal or cross-sectional data. This method may offer a way of describing 25,OHD3 deficiency between observers worldwide.
authors.affiliation: Department of Biochemistry, City Hospital, Birmingham, UK.
authors.forename: B R
authors.initials: BR
authors.lastname: Pal
authors.forename: T
authors.initials: T
authors.lastname: Marshall
authors.forename: C
authors.initials: C
authors.lastname: James
authors.forename: N J
authors.initials: NJ
authors.lastname: Shaw
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001208:Asia / Q000208:ethnology; D004739:England / Q000453:epidemiology; D005006:Ethnicity; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D012016:Reference Values; D015203:Reproducibility of Results; D012621:Seasons; D012680:Sensitivity and Specificity; D012737:Sex Factors; D013223:Statistics as Topic; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood*; D014808:Vitamin D Deficiency / Q000175:diagnosis* / Q000208:ethnology
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D