Using Elecsys® HIV Combi PT assay to identify acute and early HIV infection in a teaching hospital of southwest China

Abstract

This study is the first attempt to evaluate the use of the Elecsys® HIV combi PT assay in identifying acute and early HIV infection in southwest China. We also analyzed the extent of cutoff ratios overlap between false-positive and true-positive results to aid the identification of HIV infection, using samples from the West China Hospital in Chengdu, Sichuan Province from April 2012 to December 2013. Reactive results from a screening test were retested and all repeatedly reactive samples - if available - were confirmed with Western blot, HIV-1 p24 antigen, or HIV-1 RNA. Of 241,840 samples screened, the Elecsys® HIV combi PT assay identified 54 patients with acute and early HIV infection; 99.8% cases with cutoff index ratios ≥50 were proved to be true-positive HIV infection and 95.6% cases with cutoff index ratios <15 were falsely positive. In conclusion, the Elecsys® HIV combi PT assay can identify acute and early HIV infection, including those who might have been missed by third-generation HIV screening assays and Western blot. However, cutoff index ratios <15 are not always false-reactive results; a definitive result cannot be attained without further confirmation. In resource-poor regions where a HIV-1 nucleic acid test may be unaffordable, detection of HIV-1 p24 antigen can be an alternative strategy to diagnose HIV infection in individuals with a negative or indeterminate Western blot.

Acute HIV infection in a large teaching hospital in western China: Clinical, virological, and molecular epidemiological characteristics

“…The Elecsys HIV combi PT assay (the fourth‐generation assay) was used for screening HIV infection on Cobas e601 or Modular E170 analyzer (Roche Diagnostics, Mannheim, Germany) 14 . All initially positive (cut‐off index [COI] > 1.0) or borderline (0.9 ≤ COI ≤ 1.0) specimens were retested by the third‐generation Anti‐HIV enzyme‐linked immunosorbent assay kit (Zhuhai Livzon Diagnostics Inc, Zhuhai, China) on Freedom EVOlyzer (Tecan, Switzerland) 14 before June 2016, or by the third‐generation Anti‐HIV Colloidal gold kit (Zhuhai Livzon Diagnostics Inc) after June 2016. Western Blot (WB) HIV blot 2.2 (MP Diagnostics, Singapore) was recommended as a confirmatory test 14 .…”

“…All initially positive (cut‐off index [COI] > 1.0) or borderline (0.9 ≤ COI ≤ 1.0) specimens were retested by the third‐generation Anti‐HIV enzyme‐linked immunosorbent assay kit (Zhuhai Livzon Diagnostics Inc, Zhuhai, China) on Freedom EVOlyzer (Tecan, Switzerland) 14 before June 2016, or by the third‐generation Anti‐HIV Colloidal gold kit (Zhuhai Livzon Diagnostics Inc) after June 2016. Western Blot (WB) HIV blot 2.2 (MP Diagnostics, Singapore) was recommended as a confirmatory test 14 . HIV‐1 p24 antigens were detected by the Elecsys HIV Ag immunoassays on a Cobas e601 analyzer, while HIV‐1 RNA results were collected from the hospital laboratory information system.…”

“…The Elecsys HIV combi PT assay (the fourth-generation assay) was used for screening HIV infection on Cobas e601 or Modular E170 analyzer (Roche Diagnostics, Mannheim, Germany). 14 Figure 1). The first positive/borderline fourth-generation assay results were classified as group A and the fourth-generation assay results when WB became positive were group B, thus two interrelated results for the same patient could be found in these two groups in accordance with different detection times.…”

HIV false positive screening serology due to sample contamination reduced by a dedicated sample and platform in a high prevalence environment

“…FP results usually generate LP&E S/CO signals as seen by other centres [2,6,7]. Using a combination of independent sample testing and different platform testing, for confirmation, we found that 85% of LP&E results were FP and therefore, LP&E result prevalence can be used as an indicator of FP rate.…”

“…Setting-appropriate and conservative cut-offs: The manufacturer regards a signal/sample cut-off (S/CO) > 1 as positive (4). However, based on local verification and data from other sites, a S/CO from 0.9-3) is regarded as equivocal (E), 3-30 as low positive (LP) and � 30 as positive (P) [6].…”