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. 2014 Sep 16;11(9):e1001725. doi: 10.1371/journal.pmed.1001725

Figure 2. Test characteristics of the point-of-care CD4 test as determined by model output.

Figure 2

At the time of HIV diagnosis and immunologic staging, the model captures both the “true CD4 count” of the patient and the “observed CD4 count,” or CD4 test result. The observed CD4 test result has variability around the true CD4 count, depending on the test itself (e.g., point-of-care CD4 test with precision of 32.6% CV). (A) Using model output, we calculate the sensitivity (i.e., observed CD4 count ≤250/µl, true CD4 count ≤250/µl) and specificity (i.e., observed CD4 count >250/µl, true CD4 count >250/µl) for point-of-care CD4 tests when policy sets ART eligibility at CD4 count ≤250/µl. (B) In a scenario in which ART eligibility is at CD4 count ≤350/µl, we use model output to calculate the sensitivity (i.e., observed CD4 count ≤350/µl, true CD4 count ≤350/µl) and specificity (i.e., observed CD4 count >350/µl, true CD4 count>350/µl) for point-of-care CD4 tests.