Detection of recombinant dengue virus 2 NS1 protein in Aedes aegypti mosquitoes using commercial Dengue NS1 ELISA kit

Dengue, a vector-borne disease remains as one of the most serious public health problems globally. Incidence of this disease is on an increasing trend and currently over a billion people in tropical and subtropical regions are at risk. In the absence of an operational vaccine, prevention of dengue virus (DENV) is primarily focused upon controlling mosquito vectors. Mosquito vector surveillance programmes require simple and rapid tools to detect mosquitoes infected with DENV. Here, we tested the commercially available DENV Detect™ NS1 ELISA kit (InBios International, Inc.) for detection of recombinant DENV-NS1 protein in Aedes mosquito samples. The kit was evaluated to find out the minimum detection limit of recombinant DENV-2 NS1 protein following the manufacturer’s instructions. Initially, the NS1 protein detection threshold of the kit was determined and later the assay was standardized for detection of NS1 protein in Aedes aegypti mosquito pools containing 5, 10 and 25 mosquitoes. The ELISA kit displayed high sensitivity towards detection of recombinant dengue virus-2 NS1 protein in mosquito pools (up to 25 mosquitoes per pool) at 25 pico gram concentration. Since the commercial NS1 ELISA is highly sensitive and follows a very simple procedure, it could be employed for DENV surveillance in Aedes aegypti mosquitoes, after carrying out laboratory and field bioassays with DENV infected specimens.

Analytical and Clinical Validation of Six Commercial Middle East Respiratory Syndrome Coronavirus RNA Detection Kits Based on Real-Time Reverse-Transcription PCR

BACKGROUND: During the 2015 outbreak of Middle East Respiratory Syndrome coronavirus (MERS-CoV), six different commercial MERS-CoV RNA detection kits based on real-time reverse-transcription polymerase chain reaction (rRT-PCR) were available in Korea. We performed analytical and clinical validations of these kits. METHODS: PowerChek (Kogene Biotech, Korea), DiaPlexQ (SolGent, Korea), Anyplex (Seegene, Korea), AccuPower (Bioneer, Korea), LightMix (Roche Molecular Diagnostics, Switzerland), and UltraFast kits (Nanobiosys, Korea) were evaluated. Limits of detection (LOD) with 95% probability values were estimated by testing 16 replicates of upstream of the envelope gene (upE) and open reading frame 1a (ORF1a) RNA transcripts. Specificity was estimated by using 28 nasopharyngeal swabs that were positive for other respiratory viruses. Clinical sensitivity was evaluated by using 18 lower respiratory specimens. The sensitivity test panel and the high inhibition panel were composed of nine specimens each, including eight and six specimens that were positive for MERS-CoV, respectively. RESULTS: The LODs for upE ranged from 21.88 to 263.03 copies/reaction, and those for ORF1a ranged from 6.92 to 128.82 copies/reaction. No cross-reactivity with other respiratory viruses was found. All six kits correctly identified 8 of 8 (100%) positive clinical specimens. Based on results from the high inhibition panel, PowerChek and AccuPower were the least sensitive to the presence of PCR inhibition. CONCLUSIONS: The overall sensitivity and specificity of all six assay systems were sufficient for diagnosing MERS-CoV infection. However, the analytical sensitivity and detection ability in specimens with PCR inhibition could be improved with the use of appropriate internal controls.

Evaluation of Two Commonly Used Commercial Immunochromatographic and ELISA Screening Kits for the Detection of Anti-HCV Antibodies among Patients in North Central Nigeria.

Background: Hepatitis C Virus infection presents a major public health threat globally. The advent of different immunoassays for the detection of specific markers for the diagnosis of the infection since the discovery of the virus is a positive development, but their varied degrees of sensitivity and specificity is a matter of public health concern. Aim: To evaluate the efficiency of two commercial rapid test kits for the detection of anti- HCV antibodies against a third generation Enzyme Immunoassay (EIA) used as a gold standard. Methodology: A total of 500 patient plasma samples screened by ELISA (Autobio Diagnostics, China) were subjected to further screening using two rapid test (immuno chromatographic) strips supplied by Global Diagnostics (USA) and Wondfo Biotech Diagnostic Products (China). Results: Of the 500 samples, anti HCV was detected in 79(15.80%) by ELISA, 59(11.80%) by Wondfo strip, whereas only 45(9.00%) by Global strip method. This gave Wondfo Kit a sensitivity of 75.0%, specificity of 99.0%, overall accuracy of 95.2%, positive predictive value of 93.6%, negative predictive value of 95.4% positive likelihood ratio of 75.0, negative likelihood ratio of 0.25 and Kappa value of 0.803, while Global Kit had a sensitivity of 57.0%, specificity of 100.0%, overall accuracy of 93.2%, positive predictive value of 100%, negative predictive value of 92.5%, positive likelihood ratio of 0.57, negative likelihood ratio of 0.43 and Kappa value of 0.672. Conclusion: The result pattern reveals a marked or significant variation in sensitivity of the test kits. It is therefore recommended that third generation ELISA should be used for blood donors screening, to reduce transmission of hepatitis C virus through blood transfusion. Where the use of ELISA is practically unavailable in health facilities like in remote rural areas or poorest developing countries, the used of rapid strips can be adopted provided their performance are validated before its adoption. We recommend the use of PCR for detection of HCV RNA as a supplement to ELISA in laboratories or blood banks that can afford it.

Clinical Usefulness of Helicobacter pylori IgG Ab Assay: Comparison of Six Commercial Kits / 대한임상병리학회지

BACKGROUND: The diagnostic significance of the serological detection of antibodies to Helicobacter pylori (H. pylori) has been reported by many investigators. But the comparison data between the various serological kits were not established in Korea. METHODS: Forty nine patients with upper gastrointestinal symptoms were studied from June 1997 to September 1997 in Yonsei University College of Medicine, Severance hospital. Endoscopic gastric biopsy specimens were obtained for microscopic examination of the bacteria and rapid urease test (CLO test). The sera of these patients were obtained for the serological test at the same time. The six commercial kits (Cobas Core II, G.A.P. test IgG, PYLORAGEN, QuickVue, BIOCARD Helicobacter pylori IgG, EZ-H.P.) for the detection H. pylori antibodies were evaluated for diagnosis and screening of H. pylori infection. RESULTS: Sensitivities for the six kits were from 71% to 96%, specificities were from 24% to 71%, positive predictive values were from 68% to 81%, negative predictive values were from 60% to 80%, respectively. There were statistically significant differences in four groups, between G.A.P. test and Cobas Core, G.A.P. test and PYLORAGEN, QuickVue and Cobas Core, QuickVue and PYLORAGEN. CONCLUSIONS: Sensitivities and specificities obtained in different studies revealed as great differences in the results with the same kits as between the results obtained with different kits in the same study. So, the serologic method alone for the diagnosis of H. pylori infection is not recommended. But in the screening of H. pylori infection, it can be used, because sensitivities and negative predictive values are relatively high.