Background: The measurement of vitamin D is now commonplace for preventing osteoporosis and restoring an appropriate concentration that would be effective to counteract the occurrence of other human disorders. The aim of this study was to establish whether blood sampling seasonality may influence total vitamin D concentration in a general population of Italian unselected outpatients.
Methods: We performed a retrospective search in the laboratory information system of the University Hospital of Parma (Italy, temperate climate), to identify the values of total serum vitamin D (25-hydroxyvitamin D) measured in outpatients aged 18 years and older, who were referred for routine health check-up during the entire year 2014.
Results: The study population consisted in 11,150 outpatients (median age 62 years; 8592 women and 2558 men). The concentration of vitamin D was consistently lower in samples collected in Winter than in the other three seasons. The frequency of subjects with vitamin D deficiency was approximately double in samples drawn in Winter and Spring than in Summer and Autumn. In the multivariate analysis, the concentration of total vitamin D was found to be independently associated with sex and season of blood testing, but not with the age of the patients.
Conclusions: According to these findings, blood sampling seasonality should be regarded as an important preanalytical factor in vitamin D assessment. It is also reasonable to suggest that the amount of total vitamin D synthesized during the summer should be high enough to maintain the levels > 50 nmol/L throughout the remaining part of the year.
Uvod: Merenje vitamina D danas se uobičajeno obavlja radi prevencije osteoporoze i uspostavljanja odgovarajuće koncentracije koja bi efikasno sprečila nastanak drugih ljudskih bolesti. Cilj ove studije bio je da se ustanovi da li sezona, odnosno godišnje doba u kom se uzorkovanje vrši može uticati na koncentraciju ukupnog vitamina D, u opštoj populaciji neselektovanih italijanskih pacijenata.
Metode: Sproveli smo retrospektivnu pretragu u laboratorijskom informacionom sistemu Univerzitetske bolnice u Parmi (Italija, umerena klima), kako bismo utvrdili koje su vrednosti ukupnog vitamina D (25-hidroksivitamin D) u serumu izmerene kod nehospitalizovanih pacijenata starih 18 godina i više, upućivanih na rutinske zdravstvene preglede tokom čitave 2014. godine.
Rezultati: Ispitivana populacija sastojala se od 11 150 nehospitalizovanih pacijenata (prosek godina 62; 8 592 žena i 2 558 muškaraca). Koncentracija vitamina D bila je dosledno niža u uzorcima uzetim tokom zime nego tokom ostala tri godišnja doba. Učestalost ispitanika sa nedostatkom vitamina D bila je otprilike duplo veća u uzorcima uzetim u zimu i proleće nego u leto i jesen. Multivarijaciona analiza pokazala je da je koncentracija ukupnog vitamina D bila nezavisno povezana s polom i sezonom testiranja krvi, ali ne sa starošću pacijenata.
Zaključak: Prema ovim nalazima, sezonu uzrokovanja krvi treba posmatrati kao važan preanalitički faktor u proceni vitamina D. Takođe, ima smisla pretpostaviti da bi količina ukupnog vitamina D koji se sintetiše tokom leta trebalo da bude dovoljna da se održe nivoi > 50 nmol/L tokom preostalog dela godine.
Keywords: biological variability; preanalytical variability; seasons; vitamin D.