Vitamin D testing: advantages and limits of the current assays
European Journal of Clinical Nutrition (2020)
Barbara Altieri, Etienne Cavalier, Harjit Pal Bhattoa, Faustino R. Pérez-López, María T. López-Baena, Gonzalo R. Pérez-Roncero, Peter Chedraui, Cedric Annweiler, Silvia Della Casa, Sieglinde Zelzer, Markus Herrmann, Antongiulio Faggiano, Annamaria Colao & Michael F Holick
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
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 (about 13 dollars in quantity) – Feb 2018 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
Vitamin D blood test misses a lot
See also web
- Vitamin D Measurement, the Debates Continue, New Analytes Have Emerged, Developments Have Variable Outcomes - Nov 2019, Free PDF DOI: 10.1007/s00223-019-00620-2
Download the PDF from Vitamin D Life
Expect the blood test result to be +- ~10%
Vitamin D deficiency and insufficiency has become a pandemic health problem with a consequent increase of requests for determining circulating levels of 25-hydroxyvitamin D [25(OH)D]. However, the analytical performance of these immunoassays, including radioimmunoassay and ELISA, is highly variable, and even mass spectrometric methods, which nowadays serves as the gold standard for the quantitatively determination of 25(OH)D, do not necessarily produce comparable results, creating limitations for the definition of normal vitamin D status ranges. To solve this problem, great efforts have been made to promote standardization of laboratory assays, which is important to achieve comparable results across different methods and manufacturers. In this review, we performed a systematic analysis evaluating critically the advantages and limits of the current assays available for the measure of vitamin D status, i.e., circulating 25(OH)D and its metabolites, making suggestions that could be used in the clinical practice. Moreover, we also suggest the use of alternatives to blood test, including standardized surveys that may be of value in alerting health-care professionals about the vitamin D status of their patients.
Sections of the PDF
Clipped from PDF
Dried blood spots (DBSs)
Although serum and plasma are standard for measuring the circulating 25(OH)D concentration, DBSs are increasingly exploited in large-scale epidemiological studies [97, 98]. There is good agreement between measurements of 25(OH) D from DBS and plasma, which makes DBS an accurate and robust method that can be used to screen 25(OH)D concentrations [99-102]. Also, the use of DBS for measuring 25(OH)D offers several advantages over serum or plasma. Collection of blood spots is minimally invasive.
Only a small volume is required for the extraction and quantification of 25(OH)D [103]. In addition, DBSs require no refrigeration and are stable in the dark at room temperature, are suitable for long-term storage, and can be easily transported. This creates many opportunities in medical research; for example, DBS routinely collected on Guthrie cards at birth can be used to determine how neonatal vitamin D status affects health outcomes later in life