Hospitalized Patients And Quantiferon (Positive Control Failure) Non-Diagnostics At Harlem Hospital

SESSION TITLE: Education, Research, and Quality Improvement Posters SESSION TYPE: Original Investigation Posters PRESENTED ON: October 18-21, 2020 PURPOSE: Quantiferon-TB Gold Plus (QFT-Plus) is the newest (1) Interferon Gamma Release Assay (IGRA) used to screen for latent Mycobacterium tuberculosis (MTB). It supplants previous IGRAs. QFT-Plus has a four tube (as opposed to three tubes) series with nil (negative control), mitogen (positive control), and two tubes to determine MTB positivity called TB1(CD-4 sensitive) and TB2(CD-4 and CD-8 sensitive). The value of the new test in hospitalized patient is unknown. Negative and positive testing is valuable for clinicians. However, indeterminate testing gives no useful information. The purpose of this one-year survey was to determine test usefulness in one hospital. METHODS: All QFT-Plus were evaluated in hospitalized patients from January to December 2019. Testing ordered at discretion of admitting physician. When mitogen – nil is < 0.5 IU/ml test is indeterminate (per manufacturer). Indeterminate defined as positive control failure. Data mean + S.D. or Odd Ratio (OR) + 95% C.I. RESULTS: There were 228 tests in 218 patients. The ten repeats were unchanged and excluded from analysis making 218 valid tests. There were 120 female and 98 males with mean age 47.2 + 17 years. Age range from 18 to 88. Of included tests, 66/218 were indeterminate (30.3%). There were 22 positive tests and 130 negative tests resulting in 152/218 tests (69.7%) with usable results. HIV infection was present in 28 subjects, unknown in 41 subjects, and 149 subjects were HIV negative. Thirteen of the indeterminate QFT-Plus results were in subjects with HIV infection. One positive QFT-Plus was in an HIV positive patient. Fourteen negative Quantiferons were in HIV positive patients. Excluding subjects with unknown HIV status (n = 41) gave an OR 2.53 (1.10 to 5.80). This means those with HIV infection were 2.5-fold more likely to have an indeterminate QFT-Plus compared to without HIV infection. CONCLUSIONS: Quantiferon positive control failure defined 30% of tests as indeterminate. Therefore, QFT-Plus often not helpful. Reasons for indeterminate results are unclear. Possibilities for reduced mitogen response include transport problems after blood drawing (the lymphocytes get too hot (summer) or cold (winter) ) with subsequent reduced activity or reduced cell mediated immunity (such as HIV infection). Previous positive control failure by Quantiferon reported as 5% or less. CLINICAL IMPLICATIONS: Testing by PPD can be used as an alternative. Otherwise, clinical evaluation and radiologic imaging can be utilized to evaluate for MTB. Reference: 1. Lee M-R, et. al. CD8-response by QFT-Plus/TB disease status. Journal/Infection 2019;78:299-304. DISCLOSURES: No relevant relationships by Sai Achi, source=Web Response No relevant relationships by Gene Pesola, source=Web Response No relevant relationships by Harseerat Rataul, source=Web Response