Screening for vitamin D deficiency has proliferated in recent years, and diagnostic laboratories are struggling to keep up. However, lab technicians, may be able to omit at least one sample preparation step that was long thought essential to getting an accurate reading on vitamin D levels for patients.

According to a new KAIMRC report, there is no need to vortex blood samples ahead of measuring concentrations of 25-hydroxyvitamin D, the active form of vitamin D in the body. The study also found that tubes of serum — the yellowish fluid left behind when cells and clotting factors are removed from the blood — can be analysed immediately or stored frozen for up to 30 days without affecting test results.

To help deal with the increased workload, KAIMRC clinical biochemist, Anwar Borai, now recommends diagnostic service providers skip the vortex mixing step recommended for vitamin D testing in most procedure manuals. “This will save time for the lab techs in clinical and research laboratories without affecting results,” says Borai, who led the study. 

Putting tubes in a vortex mixer may only take around 10 seconds per sample. But with huge numbers of tests now performed each year, those seconds quickly add up. Doing away with blending samples could free technicians to analyse many more samples — and thereby help identify more individuals who could benefit from vitamin D supplementation.

This could be especially important in Saudi Arabia where around 80% of the population suffers from vitamin D deficiency. Low levels of the vitamin seem counterintuitive since the region has ample sunshine, a natural source of energy for vitamin D synthesis in the skin. But with extreme temperatures and cultural practices forcing many people indoors, low levels of vitamin D are common, increasing the risk for bone fractures, diabetes and heart disease, among other health problems.

Scrutinizing the need for certain storage and mixing conditions, Borai and his students from the KAIMRC-affiliated King Saud bin Abdulaziz University for Health Sciences (KSAU-HS) in Jeddah, performed standard vitamin D assays on 31 patient samples, both with and without vortexing and with up to 30 days of cold storage. Statistically speaking, they observed some significant differences in 25-hydroxyvitamin D concentrations, depending on mixing status and the length of time in the freezer. However, as judged by vitamin D analytical quality-control guidelines, the differences were too small to be clinically significant, Borai says.

His team published their findings in the February 2020 issue of Journal of Clinical Laboratory Analysis.

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