Telomeres are the quintessential lab test for quantifying biological age. But not all telomere tests are created equal as some disparity exists between labs. Measuring small amounts of DNA in a telomere takes some skill so it is imperative to use a lab that is experienced in telomere testing.
SpectraCell was the first lab to commercialize telomere testing in the United States, back in 2010. With over a decade of samples, our reference population is well over 15,000 patients.
But there is another big difference in telomere testing in American Laboratories – that is, the sample type used for the test. In a nutshell, commercially available telomere tests might use one of the following:
- BLOOD collected via venipuncture - This is whole circulating venous blood, which is the foremost method used in thousands of studies on leukocyte telomere length and diseases.The cell on which telomeres are measured are leukocytes, a type of white blood cell. This is what SpectraCell uses.
- BLOOD collected via finger prick (dried blood spot) - This is capillary blood that is dried onto a special paper and sent to the lab as dried blood spot.It is also measuring telomeres on leukocytes.
- BUCCAL SWAB - This sample is taken using a buccal (cheek) swab that removes epithelial cells from the inside of the mouth through physical abrasion, like with a toothbrush type tool. Telomeres are measured on buccal cells, which are epithelial cells from the inside of the mouth.
- SALIVA - This is basically spit. This type of sample will contain a mixture of both buccal cells (epithelial cells in the cheek) and leukocytes.
This begs the question – how do these sample types compare to each other? In a nutshell, they don’t. Here is what we absolutely know:
Telomere measurement from blood collected via venipuncture correlate superbly with the thousands of studies on telomere length and various diseases, particularly diseases of aging. Practically all the research was done on this type of sample – leukocytes from blood collected in the vein.
We know this type of sample has the best clinical correlation. Numerous epidemiological and population studies have used whole blood for telomere length measurement, connecting telomere length to diseases of aging. And if the telomere measurement doesn’t clinically correlate, what’s the point in measuring it?
Okay, so what about saliva or buccal swab? In short, these types of tissues don’t correlate well to whole blood collected via venipuncture. We know cheek cells aren’t representative of systemic aging. They have different turnover rates and simply are not representative of the biological aging seen in whole blood telomere measurements. Remember, buccal swab is mainly epithelial (skin) cells. Saliva is a mixture of epithelial and white blood cells. For decades, studies have been done on white blood cells. It’s not a big surprise that they don’t correlate well.1
Moving on to blood – venipuncture vs finger stick. Intuitively, these seem like they would correlate more than cheek cells since, at the very least, both types of sample collection measure telomere length on leukocytes in the blood. Here’s where it gets interesting. Capillary blood is different than venous blood. When the sample is collected via fingerstick, it is mostly capillary blood. If you compare telomeres measured on blood from fingertip prick to blood from veins, the telomeres in the fingerstick blood are significantly higher.2
To complicate things further for fingertip collected dried blood spot (DBS), research suggests that the inter-assay variation is higher in dried blood spots compared to venous blood.3 One theory is that DBS may have a lower concentration of leukocytes, and this has been shown to influence the accuracy of qPCR (the technology used for the majority of commercial telomere testing).4
The take home message here: Telomere testing should be done on whole blood collected via venipuncture. The research supports this. Telomere length is not consistent across all biological sample types or methods of sample collection. The sample type will significantly influence telomere measurement.5
So, if the samples types 2,3 & 4 above are inferior, why use them? SpectraCell makes the argument that you shouldn’t. But the advantage of easy sample collection is tempting. It is easier to get a finger prick blood spot or swab the inside of your cheek than it is to have a phlebotomist draw blood from the vein. But as a lab, SpectraCell positions its testing on scientific validity. SpectraCell maintains that the inconvenience of a blood draw is worth the clinical relevance of an accurate result.
1Stein J. A comparison of telomere lengths derived from buccal and whole blood samples via qPCR. Anti-Aging Medical News; 2016:66-69.
2Zanet et al. Blood and dried blood spot telomere length measurements by qPCR: assay considerations. PLoS One 2013;8:e57787.
3Lin et al. Telomere length measurement by qPCR – Summary of critical factors and recommendations for assay design. Psychoneuroendocrinology 2019;99:271-278.