Is Immuno-PCR Better than ELISA Test for Detection of Toxoplasma gondii IgG Antibody?

INTRODUCTION: IgG antibodies against T. gondii persist for years, and can act as a reliable serological biomarker for the diagnosis of previous exposure to this parasite. Hence, the current investigation was designed to compare diagnostic power of immuno-polymerase chain reaction (iPCR) and enzyme-linked immunosorbent assay (ELISA) methods for detection of T. gondii IgG antibody. METHODS: Immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies against T. gondii were measured by the ELISA method in 81 participants. In addition, detection of acute and chronic toxoplasmosis was performed via the ELISA IgG avidity. The set-up of iPCR was carried out and then, serum IgG of subjects were detected using the iPCR method. RESULTS: Of 81 samples, 4 (4.9%) and 30 (37%) cases were be found positive for IgM and IgG against T. gondii in the ELISA method, respectively. Moreover, of 81 specimens, 42 (51.9%) and 39 (48.1%) samples had low-avidity IgG and high-avidity IgG by the IgG avidity kit, respectively. While, 59 (72.8%) of 81 samples were detected positive using the iPCR technique. Kappa (κ) value coefficient, between the iPCR and ELISA (for IgG) showed a strong agreement (0.360, p value < 0.001). A value of 0.25 I.U./ml for serum IgG [area under curve (AUC) = 0.720 (CI = 0.613-0.827); p = 0.002] was the cut-off value to differentiating between positive and negative toxoplasmosis (with sensitivity 66.0% and specificity 60.0%). CONCLUSION: Our findings indicated despite a strong agreement shown between iPCR and ELISA methods, the diagnostic power of iPCR technique was more sensitive than ELISA test for detection of T. gondii IgG antibody. However, more complementary investigations are widely needed in this regard.

Higher prevalence of Blastocystis hominis in healthy individuals than patients with gastrointestinal symptoms from Ahvaz, southwestern Iran.

BACKGROUND: Blastocystis, a common intestinal protozoan of humans and animals, infected more than 1 billion people around the world. This enteric protozoan is frequently reported in both healthy individuals and patients with gastrointestinal (GI) symptoms. METHODS: Three hundred and forty-five fecal samples including 151 GI patients and 194 healthy individuals were examined by microscopy, culture and PCR-sequencing techniques to determine Blastocystis frequency and subtype (ST) variation. RESULTS: The occurrence of Blastocystis was detected 56 (16.2%) and 85 (24.6%) by microscopy, culture and PCR methods, respectively. Out of the 85 positive patients, 60 (70.6%) were asymptomatic and 25 (29.4%) were symptomatic. The results of 41 successfully sequenced isolates identified 8 (19.5%), 8 (19.5%), and 25 (61.0%) ST1, ST2, and ST3, respectively. CONCLUSION: This study has found that Blastocystis was more common in healthy individuals than GI patients. Another finding was that no correlation was found between clinical symptoms and Blastocystis STs.