A 48‐year‐old man without significant medical history presented to our hospital with 3 weeks of increasing abdominal girth. Imaging revealed moderate ascites as well as extensive omental and peritoneal implants, diffuse lymphadenopathy, and multiple foci of hypermetabolic uptake above and below the diaphragm. Paracentesis fluid and bone marrow biopsy demonstrated a CD10‐positive, kappa‐restricted B‐cell lymphoma. Supraclavicular lymph node biopsy revealed a Burkitt‐like lymphoma. During evaluation of this patient's new lymphoproliferative disorder, his HIV‐1 ELISA test returned positive. At our institution, HIV viral load testing is performed weekly, and Western blot testing is performed every 2 weeks; at the time of antibody positivity, confirmatory testing was 6 days away. Because of this delay, we attempted to use other methods to confirm the diagnosis of HIV. An absolute CD4 count returned low, at 192 cells/μL (27%), although the patient was lymphopenic at the time of testing. The patient's Burkitt‐like lymphoma was thought secondary to underlying undiagnosed HIV infection, clinically significant, as seropositivity would affect treatment choices. While awaiting confirmatory testing, the patient was notified of his preliminarily positive HIV status. He denied any history of intravenous drug use, high‐risk sexual behavior, or blood product transfusion and had been in a monogamous relationship with his wife for 25 years. Six days after initial screening, HIV viral PCR returned undetectable, and 7 days after initial screening, the Western Blot returned negative. Chemotherapy was then initiated for his high‐grade lymphoma.
This case demonstrates that although lym‐phoproliferative disease can be the presenting sign of undiagnosed HIV infection, such a malignancy may actually be the cause of false positivity on HIV antibody testing. Common risk factors for false‐positive HIV‐1 ELISA results include autoimmune disease, renal failure, cystic fibrosis, multiple pregnancies, blood transfusions, liver disease, parenteral drug use, hemodialysis, and vaccination for hepatitis B, rabies, and influenza. Furthermore, in the setting of lymphopenia secondary to underlying hematologic malignancy, our frequent use of CD4 count as a “quick and dirty” HIV screen may be misleading in determining false versus true HIV positivity. The use of the absolute CD4 count as a surrogate marker for HIV infection is not validated and, as in this case, has the potential to result in a delay of appropriate therapy. Finally, proper treatment for patients may also be postponed while awaiting results of batched tests such as viral load and Western blot testing.
This case raises awareness of false‐positive HIV antibody testing in the setting of lympho‐proliferative disease, underscores problems that can arise from using absolute CD4 count as a surrogate marker of HIV infection, and highlights the delay in diagnosis and care that can arise from batched in‐hospital tests.
L. Haber ‐ none; S. Ranji ‐ none
To cite this abstract:Haber L, Ranji S. Cause or Effect?. Abstract published at Hospital Medicine 2011, May 10-13, Dallas, Texas. Abstract 290. Journal of Hospital Medicine. 2011; 6 (suppl 2). https://www.shmabstracts.com/abstract/cause-or-effect/. Accessed September 20, 2019.