Agreement between IP-10 (A) and IFN-γ (B) detected in plasma and DPS samples.

<p>IP-10 and IFN-γ signals were detected in samples from 18 Quantiferon-TB positive donors; nil, antigen and mitogen samples were corrected for the dilution factor in plasma. Samples were pooled rendering a total of 54 data-points per graph. DPS concentrations were analyzed as ng/2 discs for IP-10 and IU/2 discs for IFN-γ signals (DPS) and log transformed to facilitate comparison between high (plasma) and low DPS. Each sample is represented on the graph as the average of the two measurements against the difference. The limits of agreement are specified as the average difference (bias) ±1.96 standard deviation of the difference.</p

Correlation between IP-10 detected in plasma and DPS (A), and between IP-10 detected in plasma and INF-γ detected in plasma (B).

<p>A total of 25 healthy donors were compared. Nil, CMV-antigen and mitogen samples were pooled, rendering a total of 75 data-points per graph (Spearman).</p

IP-10 responses in DBS compared to DPS.

<p>QFT-CMV test stimulated blood from 8 healthy individuals, 5 CMV responders, were used to compare IP-10 signals in DBS and DPS samples. Nil antigen and mitogen samples pooled (n = 24). <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0039228#pone-0039228-g004" target="_blank">Figure 4A</a>. Correlation analysis, (p<0.0001, Spearman); <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0039228#pone-0039228-g004" target="_blank">Figure 4B</a> Bland-Altman plot of the same data. Each sample is represented on the graph as the average of the two measurements against the difference. The limits of agreement are specified as the average difference (bias, −0.8 pg/ml) ±1.96 standard deviation of the difference, (71 pg/ml).</p

IP-10 responses in plasma and DPS.

<p>QFT-CMV responses from 26 healthy individuals (Control group 2) were divided into CMV-positive (n = 17) and CMV-negative (n = 9) based on the QFT-CMV cut off for IFN-γ suggested by the manufacturer (0.2 IU/ml).</p

Magnitude of IP-10 (A) and IFN-γ (B) responses to antigen and mitogen challenge determined in plasma and DPS samples.

<p>Optical density reading from 18 Quantiferon-TB positive donors were compared. Nil, antigen and mitogen samples were pooled, rendering a total of 54 data-points per graph. OD readings from plasma and DPS samples were plotted against the IP-10 or IFN-g concentration determined in the plasma sample corrected for the dilution factor. The optimal working range of the assay is OD 0–3, a steadily increasing regression line ensures high precision.</p

Overview of the development and validation process.

<p>Overview of the development and validation process.</p