False-positive fourth-generation HIV test associated with autoimmune hemolytic anemia. Case report

Abstract

Introduction: The fourth-generation ELISA human immunodeficiency virus (HIV) screening test has a high sensitivity and specificity >99% to detect both antigens and antibodies. Estimates are that only 0.5% yield false positive results.Case description: 61-year-old female patient with a clinical picture consisting of malaise, unquantified fever, asthenia and adynamia. Laboratory tests revealed anemia, so a Coombs test was performed, obtaining a positive result along with other findings of mixed autoimmune hemolytic anemia. Two fourth-generation ELISA HIV screening tests were performed obtaining positive results. Given the national recommendations on the diagnosis of HIV infection, a viral load was performed, which turned out to be negative, so the result was considered a false positive.Discussion: Clinical and biological factors are related to false positive results. There are descriptions about autoimmunity phenomena, such as systemic lupus erythematosus or autoimmune hemolytic anemia, with few cases in older adults.Conclusions: Rapid tests have changed the diagnosis of HIV infection worldwide; however, like any other diagnostic test, they may yield false positive results with differential diagnoses, including autoimmune hemolytic anemia.

Falso positivo de prueba ELISA para virus de inmunodeficiencia humana en un paciente diagnosticado con granulomatosis eosinofílica con poliangeítis. Reporte de un caso

“…On the other hand, the incidence of false-positive results of the fourth generation ELISA test is low (0.5%) (6). Autoimmune diseases are an important factor in the occurrence of these results, with SLE being one of the diseases most The detection of the p24 antigen is the differentiating factor of the fourth generation ELISA, and this factor is responsible for its high diagnostic efficiency.…”

“…However, cross-reactivity with small ribonucleoprotein and other retrovirus antigens has been reported, especially in patients with hemolytic anemia, leading to false positive results in these patients (6).…”

“…Although fourth generation tests are usually very effective, there may be false-positive results resulting from four main causes: technical artifacts, chronic diseases, multiparity, and unusual circumstances (3,4). The incidence of false positive results for the fourth generation ELISA is reported to be between 0.2 and 0.5% (5)(6)(7).…”

“…Chronic conditions that can lead to false positives in ELISA include autoimmune diseases such as Sjögren's syndrome, and non-autoimmune diseases such as leprosy infection or alcoholism (3). Multiple mechanisms have been proposed to explain this phenomenon, especially in patients with systemic lupus erythematosus (SLE), such as molecular mimicry, cross-reactivity, and antibody generation (5,6).…”

“…associated with false positives to date since the description of the first cases by Perentice in 1980(6). However, it was not until 1992 that Esteva et al, in a report of two cases of false positive results for HIV, proposed molecular mimicry mechanisms (described in the 1980s) as a possible explanation for this clinical phenomenon, which are accepted today (4).It has been proposed that molecular mimicry between the different autoantibodies and HIV envelope glycoproteins results in cross-reactivity.…”