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Vitamin D deficiency of a group - 15 pcnt to 48 pcnt (depends on tester used) - Nov 2017

Harmonization of serum 25-hydroxycalciferol assay results from high-performance liquid chromatography, enzyme immunoassay, radioimmunoassay, and immunochemiluminescence systems: A multicenter study

Different results by 5 types of testers on 275 blood samples

Tester Def
<11 ng
11 - 20 ng
> 20 ng
HPLC 36%30% 34%the standard
ECL-Roche 33%30%38%OK if not taking Biotin
CLIA-Diasorin 48%33%18%too low
EIA-DIAsource 15%41%41%too high
RIA-DIAsource 30%26%43%too high

   Roche reads 9 ng too high if take 10 mg of Biotin daily for a week

J Clin Lab Anal. 2017 Nov;31(6). doi: 10.1002/jcla.22117. Epub 2017 Feb 7.
Nikooyeh B1, Samiee SM2, Farzami MR2, Alavimajd H3, Zahedirad M1, Kalayi A1, Shariatzadeh N1, Boroumand N3, Golshekan E2, Gholamian Y2, Neyestani TR1.

Remarkable disagreement among different systems of 25-hydroxy vitamin D 25(OH)D assay makes decision making for both clinical and community interventions very difficult. This study aimed to harmonize the results obtained from different 25(OH)D assay systems.

A total of 275 serum samples were analyzed for 25(OH)D using DIAsource-enzyme immunoassay (EIA), DIAsource-radioimmunoassay (RIA), Roche-electrochemiluminescence (ECL), Diasorin-chemiluminescent immunoassay (CLIA), and high-performance liquid chromatography (HPLC), as the reference method. Serum intact parathyroid hormone (iPTH) was also measured in all samples. Between-system agreement and harmonization were evaluated using Bland-Altman analysis, receiver operating characteristic (ROC), and regression analysis.

Mean serum 25(OH)D concentrations and frequency distribution of vitamin D status showed a significant difference among the studied systems (P<.001 for both). Serum 25(OH)D assay results from all systems correlated with those from HPLC. As compared with HPLC, ECL showed a positive bias (+3.8 nmol/L), whereas CLIA had a negative bias (-11.9 nmol/L). Both EIA and RIA showed a more or less similar positive bias (8.0 and 8.1 nmol/L, respectively). Using serum iPTH-based 25(OH)D cutoff points, only ECL results became comparable to and without significant difference with HPLC. However, when system-specific cutoffs were defined based on HPLC results using regression equations, mean 25(OH)D and frequency distribution of vitamin D status were more harmonized compared with the other methods.

Our findings showed that with adjustment of circulating 25(OH)D based on HPLC, frequency distribution of vitamin D status, as judged by different methods, can be well harmonized with no statistically significant inter-system difference.

PMID: 28169461 DOI: 10.1002/jcla.22117

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