Comparison of four routinely used vitamin D automated immunoassays
J Med Biochem . 2021 Jun 5;40(3):277-285. doi: 10.5937/jomb0-27531.
Jindra Windrichova 1, Pavel Broz 1, Radka Fuchsova 2, Ondrej Topolcan 1, Ladislav Pecen 1, Otto Mayer 3, Radek Kucera 1
1 University Hospital Pilsen, Department of Immunochemistry Diagnostics, Czech Republic.
2 University Hospital Pilsen, Institute of Clinical Biochemistry and Hematology, Czech Republic.
3 University Hospital Pilsen, Second Internal Clinic, Czech Republic.
This study measured the Vitamin D level from 100 blood samples on 4 different testers
- Vitamin D testing accuracies, including dried blood spot – Jan 2020
- Problems with Vitamin D Testing – chapter – Aug 2019
- Vitamin D deficiency of a group - 15 pcnt to 48 pcnt (depends on tester used) - Nov 2017
- Big differences (~10 ng) in vitamin D test results, even when using the same type of tester – Aug 2015
- Huge differences in % deficient (< 30ng) depending on the tester used
- Vitamin D measurements vary with the same sample of blood – March 2014 poor repeatability
Opinion: Due to both accuracy and repeatability variations a Vitamin D test should never be trusted to be within 5 ng
Tests for Vitamin D contains the following overview/opinion
- Fact: Many countries no longer pay for more than 1 (some not pay for even a single Vit D test)
They feel that Vit D testing is not needed except for a few conditions (Rickets, etc) Japan is an exception - Fact: Vit D tests are not very accurate
The best lab tests have accuracies and repeatabilities of +-5 ng
Low cost vitamin D Blood Tests - both in lab and at home
Many lab tests have accuracies and repeatabilities of +- 10 ng - or worse
Vitamin D deficiency of a group - 15% to 48% - Fact: Low-cost office/home Vit D tests are available around the world (not US as of 2018)
Low-cost 35 ng Y/N test by Nanospeed
Low-cost Vitamin D testers (two yes-no tests for 11 dollars) - 2024 Nanospeed
Quick, free, self test for deficiency - Fact: 3 major Vit D gene problems are not noticed by Vit D tests
~ 20% of people have poor Vit D genes
Hint that Vit D not getting to cells: Vit D related diseases run in your family
Another hint - you have one of the 40 diseases which are 2X more likely if have poor genes - Fact: A Vit D test will rarely (<1 in 1000) indicate that you are getting too much
- Opinion: If only getting a single test, wait till after supplementing with Vit D
3 months after starting a maintenance dose or 4 weeks after a loading dose
Note: For many years there has been an attempt at standardizing Vitamin D measurments used for research
It appears that most hospitals/testing facilities are not "standardized"
Download the Standarization PDF from VitaminDWiki
Download the PDF from VitaminDWiki
Background: To compare four automated immunoassays for the measurement of 25(OH)-vitamin D (25-OHD) and to assess the impact on the results obtained from a healthy population.
Methods: We analysed 100 serum samples on Unicel DxI 800 (Beckman Coulter), Architect i1000 (Abbott), Cobas e411 (Roche) and Liaison XL (DiaSorin). Passing-Bablok regression and Bland-Altman plots were used for method comparison. In order to categorise the obtained values, results were categorised into the following groups: 0-25 nmol/L, 25-50 nmol/L, 50-75 nmol/L and above 75 nmol/L and compared. The percentage of samples below 75 nmol/L, and below 50 nmol/L was then calculated for every method.
Results: According to paired comparisons, each method differs from others (p<0.0001) except Cobas vs Architect, which do not show a statistically significant difference (p=0.39). The strongest correlation was found between Liaison and Architect (ρ=0.94, p<0.0001).
The percentage of samples below the recommended value of 75 nmol/L were:
| 70% | Architect |
| 92% | Liaison |
| 71% | Cobas |
| 89% | Unicel |
The percentage of samples below the value of 50 nmol/L were:
| 17% | (Architect) |
| 55% | (Liaison), |
| 28% | (Cobas) |
| 47% | (Unicel). |
Conclusions: The observed differences stem from the use of different analytical systems for 25-OHD concentration analysis and can result in different outcomes. The recommended values should be established for each assay in accorda