Authors:Konstantin Tanida, Andreas Hahn, and Hagen Frickmann
The aim of the study was a comparative evaluation of in-house real-time PCR and commercial real-time PCR (Fast Track Diagnostics (FTD), ampliCube/Mikrogen) targeting enteropathogenic bacteria from stool in preparation of Regulation (EU) 2017/746 on in vitro diagnostic medical devices.
Both 241 stool samples from patients and 100 samples from German laboratory control schemes (“Ringversuche”) were used to comparatively assess in-house real-time PCR, the FTD bacterial gastroenteritis kit, and the ampliCube gastrointestinal bacterial panels 1&2 either with the in-house PCRs as gold standard and as a test comparison without gold standard applying latent class analysis. Sensitivity, specificity, intra- and inter-assay variation and Cohen’s kappa were assessed.
In comparison with the gold standard, sensitivity was 75–100% for strongly positive samples, 20–100% for weakly positive samples, and specificity ranged from 96 to 100%. Latent class analysis suggested that sensitivity ranges from 81.2 to 100% and specificity from 58.5 to 100%. Cohen’s kappa varied between moderate and nearly perfect agreement, intra- and inter-assay variation was 1–3 to 1–4 Ct values.
Acceptable agreement and performance characteristics suggested replaceability of the in-house PCR assays by the commercial approaches.
Authors:Andreas Hahn, Andreas Podbielski, Markus M. Heimesaat, Hagen Frickmann, and Philipp Warnke
Surrogate endpoints are widely used in clinical trials, especially in situations where the endpoint of interest is not directly observable or to avoid long trial periods. A typical example for this case is frequently found in clinical trials in oncology, where overall survival (OS) as endpoint of interest and progression free survival (PFS) as surrogate endpoint are discriminated.
Based on the perspective of case definitions on surrogate endpoints, we provide a formal definition of such endpoints followed by a description of the structure of surrogate endpoints.
Surrogate endpoints can be considered as case definitions for the endpoint of interest. Therefore, the performance of surrogate endpoints can be described using the classical terminology of diagnostic tests including sensitivity and specificity. Since such endpoints always focus on sensitivity with necessarily reduced specificity, efficacy estimates based on such endpoints are in general biased.
The abovementioned has to be taken into account while interpreting the results of clinical trials and should not be ignored while planning or conducting a study.
Authors:Andreas Hahn, Rebecca Hinz, Thomas Meyer, Ulrike Loderstädt, Ottmar Herchenröder, Christian G. Meyer, Norbert Georg Schwarz, and Hagen Frickmann
Introduction: German sex workers have illegally established a prevention strategy, which consists of testing potential sexual partners with human immunodeficiency virus (HIV)-specific rapid diagnostic tests (RDTs) prior to engaging in unprotected sexual intercourse eventually performed in case of a negative test result. Based on a recently established modeling approach, the effectiveness of this strategy regarding the risk of HIV exposure was compared with protection provided by condom use.
Methods: Based on a literature search, the following assumptions were used for the calculations: an averaged 80% exposure risk reduction with a condom used during sexual intercourse, usage of a well-characterized 4th-generation HIV RDT, and a 10 day post-infection period without any measurable viral load in peripheral blood followed by a seroconversion period of about 3 weeks with 12.3% test sensitivity (antigen-specific) and only afterwards 97.3% (antibody-specific) test sensitivity.
Results: In most constellations, the HIV exposure risk in case of RDT-based prevention was lower than with condom use.
Conclusions: The RDT-based HIV exposure prevention as established by sex workers is effective in most situations. A notable weakness of the strategy is the RDTs' poor sensitivity in spite of a high transmission risk during the seroconversion stage.
Authors:Hagen Frickmann, Andreas Hahn, Stefan Berlec, Johannes Ulrich, Moritz Jansson, Norbert Georg Schwarz, Philipp Warnke, and Andreas Podbielski
Introduction: Escherichia coli and Staphylococcus aureus are important causes of severe diseases like blood stream infections. This study comparatively assessed potential differences in their impact on disease severity in local and systemic infections.
Methods: Over a 5-year interval, patients in whom either E. coli or S. aureus was detected in superficial or primary sterile compartments were assessed for the primary endpoint death during hospital stay and the secondary endpoints duration of hospital stay and infectious disease as the main diagnosis.
Results: Significance was achieved for the impacts as follows: Superficial infection with S. aureus was associated with an odds ratio of 0.27 regarding the risk of death and of 1.42 regarding infectious disease as main diagnosis. Superficial infection with E. coli was associated with a reduced duration of hospital stay by −2.46 days and a reduced odds ratio of infectious diseases as main diagnosis of 0.04. The hospital stay of patients with E. coli was increased due to third-generation cephalosporin and ciprofloxacin resistance, and in the case of patients with S. aureus due to tetracycline and fusidic acid resistance.
Conclusions: Reduced disease severity of superficial infections due to both E. coli and S. aureus and resistance-driven prolonged stays in hospital were confirmed, while other outcome parameters were comparable.
Authors:Anja Dörschug, Julian Schwanbeck, Andreas Hahn, Anke Hillebrecht, Sabine Blaschke, Uwe Groß, Markus M. Heimesaat, Hagen Frickmann, and Andreas E. Zautner
To efficiently monitor the COVID-19 pandemic for surveillance purposes, reliable serological rapid diagnostic tests (RDTs) are desirable for settings where well-established high-throughput bench-top solutions are not available. Here, we have evaluated such an RDT.
We have assessed the Xiamen AmonMed Biotechnology COVID-19 IgM/IgG test kit (Colloidal gold) and the EUROIMMUN benchtop assay with serum samples from patients with polymerase chain reaction (PCR)-confirmed COVID-19 disease. Samples from patients with Epstein-Barr-virus (EBV) infection and blood donors were used for specificity testing.
For the colloid gold rapid test and the EUROIMMUN assay, the study indicated overall sensitivity of 15.2% and 67.4%, respectively, while specificity of 99.0% and 97.9% with the blood donor sera, as well as 100% and 96.8% with the EBV-patients, were observed, respectively. An association of the time period between positive PCR results and serum acquisition with serological test positivity could be observed for the immunologlobulin G subclass of the EUROIMMUN assay only.
In spite of acceptable specificity of the assessed RDT, the detected poor sensitivity leaves room for improvement. The test results remain difficult to interpret and therefore the RDT can currently not be recommended for routine diagnostic or surveillance use.
Authors:Hagen Frickmann, Andreas Hahn, Norbert Georg Schwarz, Ralf Matthias Hagen, Denise Dekker, Rebecca Hinz, Volker Micheel, Benedikt Hogan, Jürgen May, and Raphael Rakotozandrindrainy
Direct growth on blood and screening agar for methicillin-resistant Staphylococcus aureus (MRSA) at a tropical surveillance site was compared with broth enrichment and subsequent growth on selective MRSA agar after international sample transport.
In Madagascar, 1548 swabs from an MRSA surveillance study were assessed for growth on Columbia blood agar enriched with 5% sheep blood and MRSA screening agar at the surveillance site with subsequent cold storage of the samples and shipment to Germany. In Germany, 1541 shipped samples were analyzed by non-selective broth enrichment with subsequent culture on MRSA selective agar.
A total of 28 MRSA isolates were detected. Of these, 20 strains were isolated from direct culture on blood and MRSA screening agars at the surveillance site, 24 MRSA strains were isolated using the broth enrichment method in Germany, and 16 MRSA strains were identified by both approaches.
In spite of the observed die-off of individual strains due to long-term storage and transport, broth enrichment with subsequent screening on MRSA selective agar after international sample shipment led to comparable sensitivity of MRSA detection like streaking on blood and MRSA agar at the tropical surveillance site.