Rapid serological diagnosis of melioidosis: an evaluation of a prototype immunochromatographic test

AIMS: To evaluate the Panbio melioidosis prototype (ICT) IgG and IgM test kits in detecting antibodies to Burkholderia pseudomallei from an endemic region of Australia. This would be of particular importance in high prevalence, low resource regions. METHODS: Seventy-five culture-confirmed sera for melioidosis and 158 negative control sera from subjects in North Queensland were tested. All sera samples were also tested with an in-house indirect haemagglutination assay (IHA). Seventy-three of the positive sera were further tested using an in-house EIA IgG and IgM assay. RESULTS: The Panbio IgG kits had a sensitivity of 50.6% (95%CL 38.9-62.4) and a specificity of 97.4% (95%CL 93.7-99.3). The Panbio IgM kits had a sensitivity and specificity, respectively, of 72.0% (95%CL 60.4-81.8) and 71.5% (95%CL 63.8-78.4). CONCLUSIONS: The ICT kits were found to be rapid and easier to use than current serological methods. In particular, the IgG ICT kit would have a potential role in determining existing disease in low resource regions.     

Evaluation and validation of an enzyme-linked immunosorbent assay and an immunochromatographic test for serological diagnosis of severe acute respiratory syndrome

A newly developed severe acute respiratory syndrome (SARS)-specific enzyme-linked immunosorbent assay (ELISA) was further validated to confirm cutoff values and evaluate its diagnostic performance with clinical samples. In parallel, an immunochromatographic test was also evaluated. A total of 227 clinical serum specimens collected from SARS patients were used in the study, together with 385 samples from healthy donors. By use of an immunofluorescent (IF) test as the "gold standard", both the ELISA and the immunochromatographic test were able to detect immunoglobulin G antibodies to SARS not only from late-convalescent-stage samples (>21 days from the onset of clinical symptoms), as previously established, but also from early-acute-phase samples (1 to 10 days from onset). The ELISA, using an optical density (OD) of 0.25 as its cutoff value, produced the best sensitivity while maintaining high specificity. It detected SARS-specific antibodies in 58, 70, 75, and 95%, respectively, of the four groups of samples collected from patients 1 to 10 days, 11 to 20 days, 21 to 30 days, and more than 30 days after the onset of clinical symptoms. Similarly, the immunochromatographic test detected SARS-specific antibodies in 55, 68, 81, and 79% of the four groups, respectively. The overall specificities for the ELISA and the rapid test were 99.5 and 97.7%, respectively. Although the positive correlation observed between the ELISA OD values and the IF titers was moderate (r = 0.6915; P < 0.001), the detection rates of both the ELISA and the rapid test were found well in agreement with the IF titers.     

Performance of an immunochromatographic test for the rapid diagnosis of malaria

The immunochromatographic test (ICT) for the rapid diagnosis of malaria has been marketed for several years. In a study in which three Centres of Tropical Medicine participated and data were pooled, performance of the test varied considerably when comparing the results between each centre. The sensitivity of ICT in 2,343 patients tested in our services was 100% and the specificity 99.74%. Moreover, two patients with a positive ICT would initially have been missed by expert microscopy, with Plasmodium falciparum malaria being confirmed microscopically some hours later. The principal reasons for the better performance of the test in our series appear to be blood collection in EDTA vials and considerable experience with handling and interpreting the ICT test.     

Use of recombinant envelope proteins for serological diagnosis of Dengue virus infection in an immunochromatographic assay.

An immunochromatographic test that incorporates recombinant antigens (Dengue Duo Rapid Strip Test; PanBio, Brisbane, Australia) has recently become commercially available. This assay is performed in 15 min and detects both immunoglobulin M (IgM) and IgG in a capture format. The four recombinant proteins used represent the N-terminal 80% of the viral envelope glycoproteins of dengue viruses 1, 2, 3, and 4, respectively. The sensitivity and specificity of the recombinant-antigen-based assay were 90 and 86%, respectively. The similar diagnostic performance of these antigens to that of enzyme-linked immunosorbent assays using whole dengue virus suggests that they mimic whole dengue viruses in primary structure and epitope conformation. These results suggest that recombinant proteins can be used in diagnostic assays for dengue to overcome safety issues associated with the use of whole virus.     

Usefulness of urinary antigen detection by an immunochromatographic test for diagnosis of pneumococcal pneumonia in children

We evaluated an immunochromatographic assay detecting pneumococcal antigen in urine samples from children diagnosed with pneumococcal pneumonia. The sensitivity and specificity of the immunochromatographic test with nonconcentrated urine (NCU) were 86.7 and 62.9%, respectively; with concentrated urine (CU), they were 100 and 11.7%, respectively. Pneumococcal antigen was also detected in 42.5% of NCU and 87.1% of CU samples from nasopharyngeal carriers. This is a nonspecific test for the diagnosis of pneumococcal pneumonia in children, particularly the very young.     

Assessment of a rapid immunochromatographic test for the diagnosis of norovirus gastroenteritis

Noroviruses are the leading cause of acute gastroenteritis in people of all ages. Since the viruses are highly infectious, rapid and early diagnosis is important to prevent and control the disease. The present study aimed to evaluate the commercial immunochromatographic test RIDA? QUICK Norovirus for the detection of norovirus in stool samples from patients with acute gastroenteritis in Thailand. As compared with reference RT-PCR results, the RIDA? QUICK Norovirus assay provided a sensitivity of 48.2 and 83.3% with a specificity of 87.5%. False positive results were observed in 12.5% of norovirus-negative stool samples. Based on commercial quantitative real-time RT-PCR, the RIDA? QUICK Norovirus assay revealed a highly significant association, p-value <0.001, and good agreement (kappa?=?0.6). The assay could detect norovirus in stool samples ranging from 3.22?×?10(6) to 3.26?×?10(8) copies/ml. False negative results occurred in the stool samples containing 5.9?×?10(6) copies/ml of norovirus GI or 1.85?×?10(4)?-?4.28?×?10(5) copies/ml of GII. The immunochromatographic RIDA? QUICK Norovirus assay may be useful for rapid screening of norovirus infections in patients with acute gastroenteritis in both developed and developing countries where the RT-PCR method has not been established for routine diagnosis.     

Fluorescent antibody test for the serological diagnosis of gonorrhea.

An indirect fluorescent antibody technique has been developed for the serological diagnosis of gonorrhea. The selected strain(s) of Neisseria gonorrhoeae possesses a heat-labile surface antigen (L-antigen). Sera are diluted 1:10, and an aliquot is hear inactivated at 59 C for 30 min. The treated and untreated aliquots are then examined for human immunoglobulin G anti-L-antigen. In a prelimiary study of 495 sera, 95% of those from women with a bacteriologically confirmed diagnosis of gorrhea and 87% of those from male patients were reactive in this test, whereas only 1.4% fo the sera from presumably normal individuals were reactive.     

Evaluation of the immunochromatographic CORIS Giardia-Strip test for rapid diagnosis of Giardia lamblia

The aim of this study was to evaluate the performance of the CORIS Giardia-Strip test (CORIS Bioconcept, Gembloux, Belgium) as a rapid initial method for the routine diagnosis of giardiasis. Compared to a commercial ELISA-coproantigen test (ProSpect Giardia-ELISA-microplate assay; Remel, Lenexa, KS, USA), the commercial strip test had a sensitivity of 58%, a specificity of 99%, a positive predictive value of 93% and a negative predictive value of 93% (n=158). These results are comparable to those obtained using microscopy of direct wet-mounted stool. Since the CORIS Giardia-Strip test is simpler to perform, it can replace direct wet-mounted stool microscopy for the rapid diagnosis of giardiasis; however, its sensitivity is inferior to that of other immunochromatographic antigen detection tests and fresh stool samples are required for its use. Nevertheless, the results suggest that a positive CORIS Giardia-Strip test outcome does not need confirmation, while samples with negative results should be re-examined using another, more sensitive, test.     

A comparative study of serological tests and PCR for the diagnosis of equine piroplasmosis

A total of 105 serum samples from endurance horses from different stables in Dubai were examined for the presence of antibodies against Theileria equi and Babesia caballi using immunofluorescence antibody test (IFAT) and competitive enzyme-linked immunosorbent assay (cELISA). A TaqMan real-time polymerase chain reaction (PCR) was used to detect DNA of piroplasms in specimens of clotted blood or EDTA blood samples of the same animals. Out of the 105 serum samples, the IFAT detected antibodies against T. equi in 35 (33.3%) cases while the cELISA gave 34 (32.4%) positive results. Eleven (10.5%) of the 105 sera were positive in the B. caballi IFAT while an additional five (4.8%) other specimens were diagnosed positive using the cELISA. The serological results showed that 13 (12.4%) horses had antibodies against both T. equi and B. caballi. The TaqMan real-time PCR detected DNA of piroplams in 33 (31.4%) samples while serological methods found antibodies in 38 (36.2%) horses.     

Evaluation of a rapid immunochromatographic test in the diagnosis of dengue fever

Serology is the mainstay of diagnosis in Dengue virus infection. Various rapid tests for antibody detection have been developed. They can prove to be important diagnostic tools especially in the field set up due to technical simplicity. We evaluated a Rapid immunochromatographic assay The rapid test was performed on acute phase sera collected from patients suspected to be suffering from Dengue fever/DHF. These samples were then tested by Dengue Duo Capture ELISA and compared The rapid test showed a good sensitivity for the detection of secondary dengue infection and thus can be a good screening tool.     

Development of an immunochromatographic test to detect antibodies against recombinant Em18 for diagnosis of alveolar echinococcosis

An immunochromatographic test (ICT) for the rapid detection of antibodies to Echinococcus multilocularis was developed. The ICT showed a sensitivity of 94% and a specificity of 95.4%. High degrees of agreement were observed between the ICT and an enzyme-linked immunosorbent assay (κ = 0.93) and between the ICT and immunoblot analysis (κ = 0.97). It is expected that the ICT developed in this study will be useful for the serodiagnosis of alveolar echinococcosis.     

Comparison of serological test kits for diagnosis of typhoid fever in the Philippines

We evaluated four recent antibody-detection kits for typhoid fever by using 177 febrile patients from our hospital, in 75 of whom Salmonella enterica serotype Typhi grew. TUBEX performed best, achieving 94.7% sensitivity and 80.4% specificity. Typhidot, SD Bioline Typhoid, and Mega Salmonella were less specific and, in most cases, less sensitive.     

Rapid and simple diagnosis of Chlamydophila pneumoniae pneumonia by an immunochromatographic test for detection of immunoglobulin M antibodies

To evaluate a newly developed immunochromatographic test (the MySet test) for the detection of Chlamydophila pneumoniae-specific immunoglobulin M antibodies, the results obtained by the MySet test were compared with those obtained by two serological tests. The sensitivity and specificity of the MySet test were 100% and 92.9%, respectively. The MySet test is rapid and simple to use and is thought to be a useful tool for the selection of appropriate antibiotic therapy.     

Comparison of passive haemagglutination test with Widal agglutination test for serological diagnosis of typhoid fever in an endemic area.

A passive haemagglutination test, using sheep red blood cells sensitised with Salmonella typhi lipopolysaccharide, was compared with the Widal test for the serological diagnosis of typhoid fever in an endemic area. The results obtained on sera from 152 patients with bacteriologically confirmed typhoid and 183 patients who did not have typhoid were analysed in terms of sensitivity, specificity, simplicity, and rapidity of the respective tests. The passive haemagglutination test was found to be more sensitive (80%) than the S typhi O antigen (71%) but marginally less sensitive than the H antigen (82%) of the Widal test. The false positive rate on control sera was 1.2% and 6.6%, respectively, for the Widal O and H antigens, and 1.6% for the passive haemagglutination test. Our findings indicate that the passive haemagglutination test is comparable with the Widal test for the serological diagnosis of typhoid fever in endemic areas, but is more simple, rapid, and economic. The passive haemagglutination test may be a useful alternative to the Widal test for the serological diagnosis of typhoid fever in busy microbiology laboratories in areas in which the disease is endemic.     

Evaluation of a serological test for diagnosis ofHelicobacter pylori infection in children

A serological test for the diagnosis ofHelicobacter pylori infection (Cobas Core Roche, IgG, 2nd Generation; Roche, France) was compared with the examination of biopsy samples (culture and histology) obtained after endoscopy in 115 children to assess its value. In 94 children (42 positive and 52 negative), results were concordant. In 10 children a positive serological test was associated with an absence ofHelicobacter pylori, while in 11 others a negative serological test was associated with a positive culture. Sensitivity of the test was 79.2% and specificity 83.9%. A relationship between IgG titers and age (r=0.31, p<0.05) was found. Serological tests could be useful for the diagnosis ofHelicobacter pylori infection, but a negative test result does not rule out infection, particularly in children under 10 years of age.     

Development of an immunochromatographic test strip for the detection of papaverine in pure ginger powder

A leteral-flow immunochromatographic assay was developed for the detection of papaverine (PAPA) in pure ginger powder samples. We produced a sensitive monoclonal antibody againsts PAPA (anti-PAPA mAb) by immunizing BALB/c mice with a well-characterized PAPA-keyhole limpet hemocyanin conjugate, produced in our laboratory. The coating antigen (PAPA-ovalbumin) and goat anti-mouse IgG antibody were used as the capture reagent in the control line of the test strip. Under optimized conditions, the cut-off limits of the test strip was 1?ng/mL in 0.01?M PBS (pH 7.4) and 5?ng/mL in pure ginger powder. The results were obtained within 5 min. The results revealed that the developed method is a sensitive, rapid, and simple tool for the detection of PAPA in pure ginger powder.     

Differential diagnosis of cystic and alveolar echinococcosis using an immunochromatographic test based on the detection of specific antibodies

Human cystic and alveolar echinococcoses are zoonotic diseases caused by the larval stages of Echinococcus granulosus and Echinococcus multilocularis, respectively. As the diseases are co-endemic in many areas of the world, a simple and rapid test for the differential diagnosis of cystic echinococcosis (CE) and alveolar echinocoocosis (AE) is needed. Here, we describe the development of an immunochromatographic test (ICT) using crude hydatid cyst fluid and a recombinant 18-kDa protein (rEm18) as antigens for the detection of E. granulosus and E. multilocularis antibodies in serum samples. The ICT was evaluated with serum samples from 195 echinococcosis patients from different endemic areas in northwestern China. These included 144 from CE patients, 51 from AE patients, 67 from patients with other parasitic diseases, 13 from patients with serous hepatic cysts, and 60 from healthy individuals. The sensitivity and specificity of the ICT for CE were 91.0 and 96.9 % and for AE were 98.0 and 99.3 % with diagnostic efficiencies of 94.1 and 99.1 %, respectively. No significant differences and high degrees of agreement were found between the ICT and an enzyme-linked immunosorbent assay for both CE and AE. Five serum samples from cysticercosis patients and one serum sample from a healthy control were found positive for CE with the ICT. These findings indicate that this test allows for discrimination between both forms of human echinococcosis. In conclusion, the ICT developed in this study is a promising tool for the simultaneous detection and discrimination of CE and AE. This test will be useful for serodiagnosis of CE and AE in clinical settings and screening programs.