If you are being tested, you might view it as an experiment and not take the result too seriously.  Telomere research itself is not new (there are roughly 20,000 published journal articles on the subject probably more than many widely accepted biomarkers). We know how to interpret results statistically when inferring about risk to a large sample of people.  However, while short telomeres statistically are related to greater disease risk among a large group, it is not clear how much the measure you get means to you, as an individual.  It is not a diagnosis, it is not deterministic, and part of the result could be due to measurement error. 

It is always possible that a measure has a significant error in it. The error could be introduced at many stages–so if you were to take different measures over time to compare them, you will want to take measures at the same time of day, and not have been sick recently. The error can happen at different points, such as when taking the sample, small procedures that vary in how the blood draw lab processes the blood, transports, and stores it. Differences in measurement can also result from different DNA extraction methods or issues with the assay.* Some measurement methods of telomere length are more reproducible and more accurate than others due to extensive clinical validation and experience of the technicians of a particular laboratory. Some assay methods are validated to regulatory standards.  In the US, Lab Developed Tests are regulated by the Center for Medicare Services under the Clinical Laboratory Improvement Amendments (CLIA) of 1988. All of the 4 labs below are CLIA certified.

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*PREANALYTICAL CONDITIONS AND DNA ISOLATION METHODS AFFECT TELOMERE LENGTH QUANTIFICATION IN WHOLE BLOOD A TOLIOS, D TEUPSER, LM HOLD, PLOS ONE, 2016.

Different methods have different advantages and disadvantages.  The qPCR assay method of measuring telomere length has been the assay method most frequently published in the vast majority of publications on humans so we know most about it.  The various methods get results that are highly correlated, so they are roughly telling the same story (ie, to give you a sense of whether you have short, average, or long telomeres). The non-qPCR methods below that use imaging (fluorescence) tend to be more expensive and more accurate at the low end of the assay. Such tests are often requested by clinicians who want to know if their patients have very short telomeres, observed in genetic disorders that directly impact on telomere length. 

There are no clear hard cut-offs for what telomere length should be at each age because it is a wide range rather than a narrow range.  The reality is that in any study, telomere length varies widely by age — so while it is correlated with chronological age, this correlation is only moderate, not strong.  That means that there is overlap –- some 80-year-olds have the same telomere length as some 40-year-olds, and vice versa. For this reason, Repeat Diagnostics, one of the companies below, does not recommend that healthy individuals have their telomere length measured, due to the large variation at any given age.  It is also hard to know how companies determine what telomere length should be at any age unless they publicly share the data they are using for determining this (a study showing what the norms are that are guiding their cut-off points for age groups).  

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Telomere Diagnostics is in the process of publishing how they developed age-based norms/ The reference is Blauwkamp MN, Fasching CL, Lin J, Guegler K, Hytopoulos E, Watson D, and Harley CB. Analytical validation of relative average telomere length measurement in a clinical laboratory environment. (2017).  The Journal of Applied Laboratory Medicine (in press).

To demonstrate both how telomere length varies in normal individuals by age we show you a figure from a published paper.*  This shows norms of telomere length in lymphocytes (black) compared to granulocytes (grey), using the same assay that Repeat Diagnostics uses. You can see that there is a range (a small “cloud”) of normal values at any age, for both cell types. (Note: The PCR method uses whole blood so it measures a mix of both lymphocytes and granulocytes). 

*Figure 1 from “Collapse of telomere homeostasis in hematopoietic cells caused by heterozygous mutations in telomerase genes", G Aubert, GM Baerlocher, I Vulto, SS Poon, & Lansdorp, Plos Genetics, 2012.

Given the wide variance at any age, for an individual, actual comparisons with what may be expected at your age at one-time point might not be as meaningful as tracking how you change over time.  No one has determined what the right amount of time is to do repeat testing and there are several issues to know about, below. 

There are still many mysteries and unanswered questions in this field.  Many studies show an inverse relationship between how long your telomeres are, once they are measured, and how quickly they shorten over the subsequent months or years.  Thus, an individual with very long telomeres is more likely to show greater telomere shortening in the subsequent period, and conversely, those with very short telomeres are more likely to remain stable or undergo what looks like a period of lengthening. Part of this is thought to be due to statistical reasons –“regression to the mean” but even once this is corrected for, this relationship is still usually seen. We believe it is due in part to the normal biological regulation of telomere length. 

Regardless of initial length is, when measured in periods of less than a year, it appears that telomere length oscillates, it can lengthen or shorten.  It is unclear how much average telomere length oscillates within a person over months, and how much of this is due to measurement error, or reasons related to our daily behavior and health. While we know it does fluctuate over shorter periods of time, we don’t know how much the natural oscillations may affect any particular telomere test result. We don’t know how meaningful oscillations are that happen in short periods of time. You can see there is still a lot to learn! If you are considering testing, it may be worthwhile to test more than once to establish a more reliable baseline.

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In sum, the significance of short-term transient changes in telomere length is not fully understood.  People who learn they have short telomeres may be distressed by that, but they may also have more stable telomere length over time.  They may have longer telomeres when measured the second time, especially if it is within the next few months rather than years. 

It’s possible but highly unlikely, as these genetic conditions are very rare and typically accompanied by symptoms of early illnesses and/or having that in your family history.  We offer no medical advice here, rather a reasonable suggestion:  If you find yourself in that part of the distribution, we recommend that you talk to your physician, and decide if you want to get retested by one of the last two methods that are more accurate for determining very short telomeres.  Of course, if there are signs of a syndrome, you might want to find a physician with expertise in this area, to help determine if this is the case for you.