Comparison between enzyme-linked immunosorbent assay and indirect immunofluorescence for detection of antineutrophil cytoplasmic antibodies

Detection of IgG Anti-Giardia duodenalis Antibodies in Sera by Indirect Immunofluorescence and Western Blotting Assays

INTRODUCTION

Serological assays are alternative laboratory tools for the diagnosis of parasitic infections. The aim of this work was to evaluate the performance of the indirect fluorescent antibody test (IFAT) and Western blotting (WB) for the detection of IgG anti-Giardia antibodies in human sera.

METHODOLOGY

Sera from individuals infected with Giardia duodenalis, other parasites or non-parasitized were selected for serological assays. Ninety-seven sera were tested by IFAT at 1:20 and 1:40 dilutions and of these, 40 samples were also analyzed by WB.

RESULTS

The sensitivity and specificity of the IFAT was 97% and 46.9% at 1:20 sera dilution, and 39.4% and 59.4% at 1:40 sera dilution. The low molecular weight polypeptides fractions of 25 kDa, 27-31 kDa and 45-55 kDa were the most frequently identified by the sera of individuals infected with G. duodenalis, along with low cross-reactivity, presenting an individual sensitivity of 42.8%, 50.0% and 57.1%, and specificity of 83.3%, 83.3% and 91.7%, respectively. The highest overall sensitivity of WB (85.7%) was based on the immunoreactivity of sera with at least one of those proteins. The concordance between the detection of G. duodenalis in feces by microscopy and the WB results was considered substantial (Kappa = 0.61).

CONCLUSION

Constant exposure to Giardia infection throughout a lifetime can maintain high levels of specific antibodies in serum, even without active infection. Moreover, proteins found in intestinal amoebas may hinder the serological diagnosis of giardiasis in endemic areas due to cross-reactivity, which can be partially solved using Giardia low molecular weight proteins.

Effect of transcranial magnetic stimulation on treatment effect and immune function

To explore the effect of transcranial stimulation on the therapeutic effect and immune function of patients with post-stroke depression (PSD). Methods Selection in September 2020-April 2021 on the diagnosis of 70 patients with PSD as the research object, 35 patients were randomly divided into control group and intervention group and control group given conventional treatment, the intervention group in the control group on the basis of the application of transcranial magnetic stimulation treatment, compare the curative effect of two groups of patients after the treatment cycle and the effects on the immune function. Results After treatment, the levels of DA, NE, 5-HT in 2 groups were significantly increased, and those in the observation group were significantly higher than those in the control group (P < 0.05). After 8 weeks of treatment, serum Gly content in 2 groups was significantly increased and Glu content was significantly decreased compared with before treatment. Compared with the control group, serum Gly content in observation group was significantly increased and Glu content was significantly decreased after treatment (P < 0.05). After 8 weeks of treatment, the contents of IL-1β, IL-6 and TNF-α in serum of 2 groups were significantly decreased, compared with the control group, the contents of IL-1β, IL-6 and TNF-α in serum of observation group were significantly decreased (P < 0.05); Before treatment, there was no significant difference in PHQ-9 score and MBI score between the two groups (P > 0.05). After 8 weeks of treatment, PHQ-9 score and MBI score in the two groups were better than before treatment, and the observation group was better than the control group (P < 0.05). Conclusion Transcranial magnetic stimulation therapy can not only effectively promote the synthesis and release of monoamine neurotransmitters in patients with post-stroke depression, regulate the inhibitory/excitatory amino acid neurotransmitters, reduce inflammatory response, improve the clinical treatment effect and enhance the immune function of PSD patients, which has clinical application value.

A Comparative Evaluation of Antigen-Specific Sandwich Immunoassay and Indirect Immunofluorescence Assay (IIF) in Detecting Antineutrophil Cytoplasmic Antibodies: Are We Ready to Replace IIF with ELISA as the Primary Screening Method?

Background Antineutrophil cytoplasmic antibodies (ANCA) are important biomarkers in the diagnosis of ANCA-associated vasculitis, and indirect immunofluorescence (IIF) had been the method of choice for its detection from the very beginning. However, international consensus on ANCA testing (2017) advocates the use of high-quality immunoassays as the primary screening method. The purpose of this study was to evaluate the diagnostic performance of enzyme-linked immunosorbent assay (ELISA) compared to IIF in detecting ANCA.

Methods One-hundred eighty-nine serum samples of suspected or known cases of systemic vasculitis were screened for ANCA by IIF and proteinase-3- and myeloperoxidase-ELISA. In IIF, positive results were further divided into cytoplasmic pattern of ANCA and perinuclear pattern of ANCA, depending upon the pattern of fluorescence. McNemar’s chi-squared test was applied to check the equality of proportions of positive results, and Kappa statistics was used to measure the agreement between the two methods. Diagnostic performance of ELISA was evaluated taking IIF as reference.

Results IIF detected ANCA in 17.5% cases and ELISA detected it in 11.6% cases. A good agreement between the overall performance of ELISA and IIF was observed ( K -value: 6.8, p -value: < 001). However, a significant difference in the proportion of positive results by the two methods was observed in McNemar’s test (two-sided p -value: 0.007). Taking IIF as standard, ELISA showed 60.6% sensitivity, 98.7% specificity, and predictive value of positive and negative results of 90.9 and 92.2%, respectively.

Conclusion The new generation antigen-specific ELISAs had high specificity but the chances of missing cases in primary screening due to the low sensitivity and high false negativity (39.4%) need to be dealt with.