Effect of smoking on the serum levels of 25-hydroxyvitamin D depends on the assay employed.
OBJECTIVE
Because we found higher serum 25-hydroxyvitamin D (25(OH)D) levels among smokers than among non-smokers with analyses using an electrochemiluminescence immunoassay (ECLIA) from Roche, the purpose of the present study was to examine whether this difference between smokers and non-smokers was maintained using other serum 25(OH)D assays.


METHODS
A cross-sectional population-based study on 6932 participants from the Tromsø study, 1994-1995, and one validation study comparing six different serum 25(OH)D assays in 53 non-smokers and 54 smokers were performed.


METHODS
The association between smoking, season and serum 25(OH)D as measured by ECLIA (Roche) was assessed in the population-based study using general linear models with multivariate adjustments. In the validation study, serum levels of 25(OH)D were analysed with liquid chromatography coupled with mass spectrometry assay from two different laboratories, RIA (DiaSorin), HPLC, RIA (IDS) and ECLIA (Roche). T-tests and linear mixed model analyses were performed to compare the serum 25(OH)D levels in smokers and non-smokers within and between the methods.


RESULTS
In the population-based study, the serum levels of 25(OH)D using the ECLIA method were 51.9, 53.2 and 72.0 nmol/l in never, former and current smokers (P<0.01). In the validation study, the serum concentration of 25(OH)D was 10.3 nmol/l higher in smokers than in non-smokers (P<0.01) using the ECLIA (Roche), while non-significantly lower serum levels of 25(OH)D were found in smokers using the other five methods.


CONCLUSIONS
These two studies indicate that the ECLIA (Roche) overestimates serum 25(OH)D levels in smokers by unknown mechanisms. If confirmed, this might have clinical consequences, and the issue needs further exploration.
Grimnes
Guri
G
Medical Clinic, University Hospital of North Norway, Tromsø, Norway. guri.grimnes@unn.no
Almaas
Bjørg
B
Eggen
Anne Elise
AE
Emaus
Nina
N
Figenschau
Yngve
Y
Hopstock
Laila Arnesdatter
LA
Hutchinson
Moira Strand
MS
Methlie
Paal
P
Mihailova
Albena
A
Sneve
Monica
M
Torjesen
Peter
P
Wilsgaard
Tom
T
Jorde
Rolf
R
D000328:Adult; D000368:Aged; D002853:Chromatography, Liquid / Q000592:standards*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000592:standards*; D008297:Male; D013058:Mass Spectrometry / Q000592:standards*; D008875:Middle Aged; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D012907:Smoking / Q000097:blood*; D011795:Surveys and Questionnaires; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
D014807:Vitamin D; C104450:25-hydroxyvitamin D