One-day detection of PCR amplified Chlamydia trachomatis DNA in clinical samples: ELISA versus Southern blot hybridisation.

AIMS: To compare ELISA and Southern blot hybridisation for the detection of PCR amplified Chlamydia trachomatis DNA extracted from clinical samples; to assess the value of the ELISA method in a clinical setting. METHODS: DNA was extracted from urogenital samples of 508 patients, purified and amplified using C trachomatis specific primers, one of which was endlabelled with biotin. Amplification products were detected by Streptavidin biotin based ELISA and non-radioactive Southern blotting. RESULTS: Of the 508 samples, 29 were positive and 479 negative by both methods. No discrepant results were observed. CONCLUSION: Streptavidin biotin based ELISA and Southern blotting were equally sensitive for detecting PCR amplified C trachomatis DNA. Using ELISA, test results could be generated within a single day.

Comparison of three commercially available enzyme-linked immunosorbent assays and biopsy-dependent diagnosis for detecting Helicobacter pylori infection.

We evaluated the performance of three enzyme-linked immunosorbent assays (ELISAs) in detecting serum immunoglobulin G (IgG) and IgA antibodies to Helicobacter pylori; two were new ones from Pyloriset (Pyloriset EIA-G update and Pyloriset EIA-A update; Orion Diagnostica, Espoo, Finland), and the third was the Malakit EIA-G (Biolab, Limal, Belgium). Serum samples from 154 dyspeptic patients were collected. As a reference method, multiple biopsy specimens from different anatomical areas of the stomach were obtained by endoscopy and were analyzed by culture and/or histology and direct urease testing. Accordingly, 126 patients (82%) were found to be H. pylori positive and 28 patients (18%) were found to be H. pylori negative. To validate serology as a predictor of H. pylori infection, sensitivity, specificity, positive and negative predictive values, and accuracy of the assays were calculated against the H. pylori status as determined by the reference method. The corresponding data for the different ELISAs were 100%, 79%, 95%, 100%, and 96% for the Pyloriset ELA-G update, 81%, 89%, 97%, 52%, and 82% for the Pyloriset EIA-A update, and 87%, 86%, 96%, 60%, and 87% for the Malakit EIA-G, respectively. We conclude that the Pyloriset EIA-G update is a reliable and accurate test and that because of its 100% sensitivity, conjunctional IgA testing is not necessary. Its 100% negative predictive value makes it a very useful screening test. For purposes of excluding infection with H. pylori, the performance of the Malakit EIA-G is moderate but can be improved by conjunctional IgA testing. The Pyloriset EIA-A update can be useful as such a conjunctional test.

Serodiagnosis of Helicobacter pylori infection: an evaluation of a commercially available ELISA-IgG.

BACKGROUND: Our aim was to evaluate a commercially available ELISA (Pyloriset IgG, Orion diagnostica, Imphos B.V.) for detection of serum IgG antibodies to Helicobacter pylori. METHODS: Serum samples were taken from 154 Dutch patients. As a reference method several biopsy specimens were taken from different gastric areas for histological analysis, bacterial culture and direct urease testing. The sensitivity, specificity, positive and negative predictive values of the Pyloriset IgG were calculated as compared to the reference method. RESULTS: Of 154 patients 126 were found to be H. pylori positive (82%), 28 were H. pylori negative (18%). Using a cut-off value at a titre of 500 U/l (as advised by the manufacturer) we found a sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 81, 89, 97 and 51%, respectively. Lowering the cut-off value to 350 U/l and excluding patients aged above 70 years optimalized the performance of the Pyloriset IgG to a sensitivity, specificity, PPV and NPV of 92, 96, 99 and 72%, respectively. In the subgroup of 54 patients under the age of 45 years a sensitivity, specificity, PPV and NPV of 92, 100, 100 and 82% was found. CONCLUSIONS: The Pyloriset IgG is a simple and accurate method for detecting H. pylori infection in dyspeptic Dutch patients. The performance of this assay is improved by lowering the cut-off value (test becomes predominantly more sensitive) and excluding older patients (test becomes predominantly more specific). Therefore serology might eventually replace endoscopy or breath tests in the detection of H. pylori infection, especially in the younger age groups.