Thangarajah, Padmaloseni
(2018)
Use of paired serum sample for the diagnosis of toxoplasma infection in selected population by using elecsys toxo IgG/IgM in HUSM.
Masters thesis, Universiti Sains Malaysia.
Abstract
Introduction
Toxoplasmosis is one of the most common worldwide parasitic infection due to
Toxoplasma gondii, an obligate intracellular parasite. The mode of transmission is
through consumption of food or water or undercooked meat contaminated with the
parasite. Maternal infection with vertical transmission depends on age of gestation.
Severity of infection is during early gestation, may lead to intense complications such as
intrauterine death (IUD) or later with increased risk of congenital infection. In ocular
toxoplasmosis, reactivation of infection are common among immunocompromised and
immunocompetent patients. Serology is still the mainstay for the diagnosis of
Toxoplasma infection. Therefore, this method was applied with paired serum sample in
selected population using Elecsys Toxo IgG/IgM assay in HUSM. The paired serum
sample was to classify the infection into early, acute, reactivation, recent, latent,
possible congenital infection and passive immunity from mother. This study aimed to
describe the clinical manifestation, determine the seroprevalence classification of
infection among the selected populations, validity of the test and percentage of patient
on treatment after first and paired serum sample.
Methodology
This is a prospective cohort study held in Microbiology Laboratory, Hospital Universiti
Sains Malaysia. Paired serum sample with interval of 2 weeks for clinically suspected
cases among selected populations were collected from 1st January 2016 till 31st
December 2016. Elecsys and cobas e 601 analyser was used to perform the Elecsys
Toxo IgG/IgM ECLIA assay. The classification of infection was generated based on the
study flow chart. Patients clinical data were obtained from clinical notes or folders.
Results
A total of 482 patients with paired serum sample were included in the study. The
highest seroprevalence was in latent infection, 54%. New born or infants were majority
having passive immunity from mother and 4.3% were classified into possible
congenital infection. Ocular toxoplasmosis were mainly classified into reactivation and
latent infection. Acute infection was successfully detected especially among new born,
pregnant women and immune compromised patients. Paired serum sample were
compared to clinically confirmed cases as gold standard have given high sensitivity
(100%), low specificity (77.1%),high negative predictive value (NPV) (100%), and low
positive predictive value (PPV) (53.5%). The ROC curve analyses of paired serum
sample showed (AUC) was 0.932 (95% confidence interval between 0.802 and 1.000, p
– value 0.001). Majority of patients classified into early, acute and reactivation of
infection were treated after the first serum sample.
Conclusion
Paired serum sample using Elecsys Toxo IgG/IgM assay is a potential diagnostic test
for Toxoplasma infection due to high sensitivity and specificity. Furthermore is a good
tool to classify the infection among selection populations. The classification of infection
is mainly to provide a better understanding regarding the infection and guide the
clinician to start treatment promptly.
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