Diagnostic accuracy of the OraQuick HIV-1/2 rapid test performed on oral mucosal fluid specimens

<p>Sensitivity = 100% (95% CI 98, 100)</p><p>Specificity = 100% (95% CI 99, 100)</p><p>Positive predictive value = 100%</p><p>Negative predictive value = 100%</p><p>Positive likelihood ratio = NA</p><p>Negative likelihood ratio = 0</p

Testing algorithm and reference standard

*<p>If Western Blot was indeterminate, ELISA (enzyme-linked immuno-assay) was repeated on stored sera; if repeatedly indeterminate, the sequence was repeated with a fresh blood sample</p>*<p>Ref: CDC guidelines for rapid testing</p

HIV Testing Algorithm

<p>HIV Testing Algorithm</p

Test-retest concordance of two QFT tests performed on the same set of specimens (N = 56 paired specimens from 14 subjects)

<p>Concordance = 96.4%; κ = 0.94</p>*<p>The cut-off value for a positive QFT test was IFN-γ≥0.35 IU/mL</p><p>QFT: QuantiFERON-TB Gold In Tube®; IFN-γ: interferon-gamma.</p

Difference in QFT results (test–re-test) versus the average of QFT test and re-test results (all on the log scale).

<p>Separate plotting characters are used for each individual and the mean log-difference is shown as the broken horizontal line. We note that there tend to be more points above zero and hence the average difference (test–re-test) lies above 0, indicating higher IFN-γ results upon re-testing of the same specimens. QFT: QuantiFERON-TB Gold In Tube®; IFN-γ: interferon-gamma.</p

Within person variability of log IFN-γ responses over 4 time points (day 0, 3, 9 and 12).

<p>Separate plotting characters are used for each individual (N = 14) who underwent 4 QFT assays on days 0, 3, 9, and 12; the dashed red line indicates the cut-off for QFT test positivity. For each individual, the IFN-γ results taken on four days are plotted on the log scale. Most individuals do not cross the positive test result threshold. For two individuals (lines shown in bold) whose trajectories do cross the threshold, test results are discordant. QFT: QuantiFERON-TB Gold In Tube®; IFN-γ: interferon-gamma.</p

Within-person variability in initial QFT results (14 individuals tested 4 times on day 0, 3, 9 and 12)

<p>QFT: QuantiFERON-TB Gold In Tube®; IFN-γ: interferon-gamma</p>*<p>The cut-off value for a positive QFT test was IFN-γ≥0.35 IU/mL</p

Test versus re-test QFT results expressed as IFN-γ (IU/mL).

<p>Data for each individual is plotted with different symbols, and the line of equality is shown as the diagonal. Note that more points fall above the line of equality than below, indicating higher IFN-γ levels upon re-testing of blood. The spread of the IFN-γ results from the line of equality increases with increasing IFN-γ results, indicating that a log-transformation was appropriate. QFT: QuantiFERON-TB Gold In Tube®; IFN-γ: interferon-gamma.</p

Raw data for the two individuals with discordant QFT results; both individuals had discordant between-test results and discordant within-person results^*

*<p>Complete QFT results for both individuals are shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0001850#pone-0001850-t001" target="_blank">Tables 1</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0001850#pone-0001850-t002" target="_blank">2</a></p><p>QFT: QuantiFERON-TB Gold In Tube®; IFN-γ: interferon-gamma</p