- Correlation and consistency between two detection methods for serum 25 hydroxyvitamin D levels in human venous blood and capillary blood.
- 4 popular vitamin D testers gave very different results (no surprise) – June 2021
- Big differences (~10 ng) in vitamin D test results, even when using the same type of tester – Aug 2015
- Vitamin D measurements vary with the same sample of blood – March 2014 poor repeatability
- Huge variation in Vitamin D test results between 4 testers for 8 people – 2013
- VitaminDWiki – Tests for Vitamin D contains:
Correlation and consistency between two detection methods for serum 25 hydroxyvitamin D levels in human venous blood and capillary blood.
Front. Nutr. 11:1291799. doi: 10.3389/fnut.2024.1291799
Yutong Xing, Kaixi Wang, Xinyu Ma, Huifeng Zhang and Xiaoyu Tian*
Department of Paediatrics, The Second Hospital Affiliated to Hebei Medical University, Shijiazhuang, China
Introduction: The study assessed the correlation and concordance of 25- hydroxyvitamin D [25(OH)D] levels in capillary and venous plasma collected simultaneously after vitamin D3 supplementation in 42 healthy adults. They were randomly divided into three groups by random number table method. Group A took 1,000 IU vitamin D3 daily, group B took 10,000 IU vitamin D3 every 10 days, and group C took 30,000 IU vitamin D3 every 30 days until the end of the 12th month. Venous blood serum 25(OH)D level was detected by chemiluminescence immunoassay (CLIA) and mass spectrometry (LC-MS) at day 1, day 14, day 28, month 6, and month 12 respectively, the capillary blood serum 25(OH)D level was detected by chemiluminescence immunoassay (CLIA) at the same time. Pearson correlation analysis and linear regression analysis were employed to investigate the relationship and transformation equation between the findings of the two samples and the results obtained from different detection methods within the same sample. The Bland-Altman method, Kappa analysis, and receiver operating characteristic (ROC) curve were utilized for assessing consistency, sensitivity, and specificity.
Results: The three groups all reached a stable peak at 6 months, and the average levels of the three groups were 49.21, 42.50 and 43.025 nmol/L, respectively. The average levels of group A were higher than those of group B and group C (P < 0.001).The mean values of serum 25(OH)D measured by LC-MS and CLIA in 42 healthy adults were 45.32 nmol/L and 49.88 nmol/L, respectively, and the mean values of 25(OH)D measured by LC-MS in capillary blood were 52.03 nmol/L, and the difference was statistically significant (P < 0.001). Pearson correlation analysis showed that the linear fitting formula of scatter data was as follows: venous 25(OH)D concentration (nmol/L) = 1.105 * capillary 25(OH)D concentration -7.532 nmol/L, R2 = 0.625. Good agreement was observed between venous and corrected capillary 25(OH)D levels in clinical diagnosis (Kappa value 0.75). The adjusted serum 25(OH)D in capillary blood had a high clinical predictive value.
Conclusions: The agreement between the two methods is good when the measured 25(OH)D level is higher. Standardized capillary blood chemiluminescence method can be used for 25(OH)D detection.
In this case, daily had better response than every 10 or 30 days
Download the PDF from VitaminDWiki
4 popular vitamin D testers gave very different results (no surprise) – June 2021
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
Huge variation in Vitamin D test results between 4 testers for 8 people – 2013
- For person #8 these was a 40 nanogram difference between testers for the same blood sample
VitaminDWiki – Tests for Vitamin D contains:
- 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