The effect of repeated freezing and thawing on T/S ratio measurements.

<p>DNA was extracted from whole blood aliquots obtained at each of seven consecutive freeze-thaw cycles and T/S ratios were determined.</p

Relative T/S ratio in anti-coagulated whole blood, anticoagulated DBS and finger prick DBS samples over many days.

<p>Relative T/S ratios in whole blood collected into three anticoagulants from a single individual on 10 different days (panel A) and DBS created from the anticoagulated whole blood and from finger prick on the same days (panel B) were highly variable.</p

Correlation between monoplex and multiplex qPCR.

<p>ACD WB (N = 32) samples were measured by monoplex and multiplex qPCR. Correlations were done between S (panel A), T (panel B) and T/S (panel C). Pearson’s R<b>²</b> and p values are shown.</p

Sample collection overview.

<p>Diagram outlining the sites of blood sample collection, anticoagulants used, sample processing, and parameters tested for each sample type.</p

Comparison of T/S measurements in DBS, PBMC and WB samples.

<p>T/S ratios were determined for DNA from DBS (n = 12), PBMC (n = 12) and WB (n = 12) samples made from a single blood draw from 12 distinct individuals. Pearson’s R<b>²</b> and p values are shown.</p

Standard curves used to determine T/S ratio.

<p>Pooled blood DNA was serially diluted (1:2) to generate nine DNA standards for the ASPG accessory gene (S) (panel A) and the telomere region (T) (panel B). Stability of the T/S ratio within the range of DNA concentrations was tested (panel C). N = 1 for each point.</p

The effect of site of blood draw on T/S ratio measurements.

<p>T/S ratios were measured for DNA from arm EDTA whole blood, arm whole bloodDBS, finger EDTA WB, finger EDTADBS and direct finger prick blood made from a single blood draw from 12 distinct individuals. P values are shown, without adjustment for multiple comparisons. ns  =  not significant (p>0.05). The line represents the median and the + represents mean.</p

Stability of T/S measurements in anticoagulated whole blood samples in different storage conditions.

<p>ACD and EDTA anticoagulated whole blood was stored at 4°C and room temperature (RT) for nine days, and daily T/S ratios are shown.</p

Relative T/S ratio (n = 10) measured in WB collected by venipuncture in various anticoagulants and DBS samples (blotted with WB or directly from the fingertip) from a single individual.

a<p>Wilcoxon signed-rank test to compare between WB and WBDBS of the same anticoagulant</p>b<p>Friedman’s test to compare anticoagulants within WB and within DBS</p>c<p>DBS made from finger prick spotted directly onto paper (no anticoagulant)</p><p>Abbreviations: T/S  =  relative telomere length ratio, SD  =  standard deviation, CV  =  coefficient of variation, WB  =  whole blood, DBS  =  dried blood spot, ACD  =  acid citrate dextrose anticoagulated, EDTA  =  Ethylenediaminetetraacetic acid anticoagulated</p