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1276. Human Immunodeficiency Virus (HIV) Diagnostic Limbo: A Retrospective Review of Discordant HIV Test Results in a Large, Academic Health Center Over a 10-Year Period to Guide Clinicians in Distinguishing False-Positive vs. Acute HIV Infection

Abstract Background The Centers for Disease Control and Prevention (CDC) recommends universal HIV screening with a fourth-generation HIV-1/2 antigen–antibody immunoassay followed by an HIV-1/-2 antibody differentiation immunoassay. Discordant results require nucleic acid testing (NAT) to distinguish acute HIV from false positives. In practice, NAT can be delayed, leaving clinicians and patients in limbo. Better understanding of factors associated with acute HIV vs. false positivity among discordant HIV tests is needed. Methods From 2014 to 2018, positive fourth-generation HIV-1/-2 enzyme-linked immunosorbent assay (ELISA) tests were retrospectively analyzed across centers in the Harris Health system in Houston, Texas. Discordant results were defined as a positive fourthgeneration HIV-1/2 ELISA with a negative HIV-1/-2 antibody confirmation test and were resolved via NAT (if possible). Duplicate results and patients with a previously positive HIV-1 viral load were excluded. Results were analyzed (Fisher’s exact test or Chi square) by year, setting (clinic/hospital), sex, age, race, and comorbid conditions (pregnancy, rheumatoid arthritis, lupus, hepatitis B and syphilis [rapid plasma reagin, or RPR>1:4] for associations with acute HIV vs. false positivity). Results Of 7,077 positive fourth-generation HIV-1/2 ELISA tests, 488 (13%) discordant cases were identified. Eighty-six (18%) represented acute HIV while 322 (66%) were false positives; 80 remained unresolved (no NAT performed). Median time to resolution via NAT was 21 days. Clinic setting, female sex, older age, non-Black race, and negative RPR status were associated with significantly higher rates of false positivity vs. acute HIV (P < 0.02 for all associations). Conclusion In this large HIV testing program in a multicenter metropolitan health system, 66% of discordant fourth-generation HIV tests represented false positives. Several clinical factors correlated with a higher rate of false positivity, likely reflecting the impact of disease prevalence on the positive predictive value of any diagnostic test. Clinicians may consider these factors when counseling their patients during the limbo period. Efforts to expedite NAT to resolve discordant cases is paramount to reducing diagnostic uncertainty. Disclosures All authors: No reported disclosures.

Background. The Southeastern United States bears a disproportionate burden of HIV infection, accounting for nearly half of all new cases. The Centers for Disease Control and Prevention released routine opt-out testing recommendations in 2006. Our emergency department collaborated with our infectious diseases clinic (ECU-ID) to implement suggested guidelines among adults since March 2017.
Methods. Our primary aim was to implement routine, opt-out HIV testing in the Vidant Medical Center Emergency Department (ED) for patients between 18 and 65 years of age who have blood work completed, and have not had a test documented in the electronic medical record (EMR) in the last year. A secondary aim was to successfully link HIV-positive patients to care at ECU-ID or preferred clinic. Methods defining programmatic success included developing nurse directed opt-out ordering protocol, integrating testing into normal ED workflow, utilizing the existing EMR to prompt testing, and hiring a linkage coordinator to initiate post-test counseling and linkage-to-care.
Results. Since March 2, 2017, a total of 7,109 HIV tests were performed; an average of 592 monthly tests conducted compared with a previous average of 10 stat tests. Testing increased 5,820% compared with 2015. Of the 21 HIV-positive patients found, 16 were newly diagnosed. Among those newly diagnosed, 14 (87.5%) were linked to care; and among the five known positives, two (40%) were linked to care. Reasons why patients could not be linked included incarceration, refusal to link to care, and re-location.
Conclusion. Joined with the implementation of a routinized ED HIV testing program, a seamless process was developed to link persons found to be positive in the ED to HIV care services; therefore, establishing a systems-level prevention model. Future plans include expanding testing to adolescents and utilizing similar methods to integrate Hepatitis C testing.
Disclosures. All Authors. Gilead Sciences, Inc.: Grant Investigator, Grant recipient and Salary. Background. While HIV and HCV testing targeted to high-risk groups results in substantially higher proportions of HIV diagnoses, universal HIV and HCV screening in emergency department (ED) settings is expected to reach populations who do not perceive themselves to be at risk or are otherwise less likely to participate in HIV and HCV testing. As a consequence the CDC recommends routine HIV screening for persons 13-64 years of age, and routine HCV screening for the birth cohort (born between 1945-1965). The objective of this analysis was to evaluate the yield of universal opt-out HIV and HCV screening in the two EDs at the University of California San Diego (UCSD).

Universal HIV and HCV Screening in San Diego
Methods. In July 2017, electronic medical record (EMR) based universal opt-out HIV screening (Architect HIV antibody [Ab]/HIV p24 antigen detection) for persons aged 13-64 years (excluding persons known HIV+ or reporteing an HIV test within the last 12 months) was implemented in our EDs. The EMR algorithm also identified HIV+ individuals who had been out of care for >12 months. In March 2018, EMR based universal HCV screening for birth cohort was added in both EDs.
Results. Over a period of 9 months 7,303 HIV tests were conducted, resulting in 24 (0.3%) new HIV diagnoses, of which 21 were successfully linked to care. In five individuals without HIV infection Architect gave a false-positive result (specificity 99.93%). In addition, the EMR algorithm identified 38 out of care HIV+ individuals of which 21 were successfully relinked to care. During the 1-month HCV birth cohort screening 963 HCV Ab tests were conducted, of which 106 (11%) resulted positive. At the time being 78 of those seropositive individuals had HCV RNA testing, of which 36 (53%) resulted positive (3.7% of all participants).
Conclusion. In San Diego, a setting with a high density of free-of charge HIV screening programs, 1/300 HIV tests in the ED yielded a new HIV diagnosis and in total 21 newly diagnosed individuals were linked to care. Identification of HIV+ out of care individuals yielded in an equivalent number of individuals relinked to care. The rate of newly diagnosed HCV infections exceeded the rate of newly diagnosed HIV infections by >10-fold outlining the importance of screening for HCV in the ED.
Disclosures. All authors: No reported disclosures.