Research Article

Delineating a Retesting Zone Using Receiver Operating Characteristic Analysis on Serial QuantiFERON Tuberculosis Test Results in US Healthcare Workers

Figure 2

Exploratory group with 575 HCWs classified as No Reversions (those with two positive tests) or Reversions (with a positive TB test result at time one and who retest negative at time two). The two groups are further classified by TBag-nil values using the ROC selected separation point of 1.11 IU/mL (Kappa = 0.48, chi-square = 131.0, ). Highlighted boxes emphasize the difference in number of No Reversions versus Reversions when TBag-nil < 1.11 IU/mL, the identified retesting zone.