J Clin Lab Anal. 2018;32:e22287. wileyonlinelibrary.com/journal/jcla
1 of 6
© 2017 Wiley Periodicals, Inc.
Accepted: 29 May 2017
A retrospective analysis of the application of the Elecsys
combi PT assay in southern China
Shaocong Liang | Guihua Deng | Shaosong Zhou | Jing Zeng |
Weiqing Tan | Xiaopeng Yuan
Department of Laboratory Medicine, Zhujiang
Hospital, Southern Medical University,
GuangZhou, GuangDong, China
Xiaopeng Yuan, Department of Laboratory
Medicine, Zhujiang Hospital, Southern
Medical University, GuangZhou, GuangDong,
Background: Fourth- generation HIV assays have been implemented worldwide as a
screening test for many years. Understanding the performance of fourth- generation
assay in low HIV prevalence region is pivotal to interpret the test result correctly. In
this study, retrospective analysis was used to evaluate application of the Elecsys
combi PT assay.
Methods: A total of 85 043 specimens from a low prevalence setting were detected
between June 2013 and October 2015. We evaluated the false- positive rate (FPR),
specificity, and positive predictive value (PPV).
Results: The specificity between male and female were 99.85% and 99.82%, respec-
tively. The PPV on male (50.75%) was higher than female (17.05%) significantly, while the
FPR was 0.15% and 0.18%. The gap between false- positive (median: 1.83, [IQR]: 1.30,
3.38) and confirmed- positive (median: 407.5, [IQR]: 184.2, 871.7) is enormous. The high-
est s/co ratio for false- positive cases was 85.45, while the lowest s/co ratio for confirmed-
positive cases was 59.68. Various reasons were attributed to false-positive cases.
Conclusion: Optimal cutoff value is needed to be set to reduce the false- positive cases
and predict the final status of HIV infection reliably. Retrospective analysis will help us
to understand more about diagnosis of HIV.
false-positive, fourth-generation HIV assays, PPV, specificity
1 | INTRODUCTION
Human immunodeficiency virus (HIV), transmitted through sexual
and percutaneous routes, is the causative agent for AIDS, the most
devastating disaster in the world.
In recent years, the patterns of
transmission about the HIV/AIDS incidence have shifted markedly in
worldwide. It is reported that nearly 501 000 people were living with
HIV/AIDS in China at the end of 2014,
while the infection increased
in MSM (men who have sex with men) and fell in IDU (intravenous
drug use) generally.
Cohort studies suggest that the rate of HIV
transmission in recent infections is much higher compared to estab-
Over the past decades, great progress has been
made in serologic assays for detection of HIV infection, especially
to permit acute HIV infection (AHI) detection.
AHI, only diagnosed
through nucleic acids, viral antigens or both, is crucial for antiretroviral
therapy and prevention of transmission.
The fourth- generation assays, which allow simultaneous detection
of p24 antigen and HIV- 1/2 antibodies, are gradually replacing third-
generation assays to shorten the diagnostic window prior to serocon-
version. In current diagnostic algorithms, the fourth- generation assays
are implemented worldwide as an initial test. Nevertheless, multiple
studies indicated that test performance may vary significantly in dif-
ferent demographic factors and geographic regions.
As understanding the performance of fourth- generation assay in
local region is pivotal to interpret the test result correctly, in the pres-
ent study, we set out to analyze the Elecsys
HIV combi PT assay in
Shaocong Liang and Guihua Deng contributed equally