Thomas Krech, MD

Biography

Thomas Krech, MD

Thomas Krech reached his MD grade at the University of Berne/Switzerland in 1981. He is Professor for Medical Microbiology and Virology at the University of Düsseldorf/Germany. He is head and owner of the Krech Group consisting of two diagnostic laboratories, a company providing quality control plasmas for the kit industry and a company offering self-testing over the internet. Professor Krech has served as a specialist in infectious diseases, hygiene and immunology at the Universities of Düsseldorf and Berne for 6 years, before he switched to the private laboratory sector 17 years ago. He has served as an officer on the Board of the European Group for Rapid Viral Diagnosis and the World Association of Societies of Pathology and Laboratory Medicine. His special interest is focused on better laboratory results by improving the technology for diagnosis of diseases.

He resides with his family in Switzerland.

Sampling of Chlamydia trachomatis and Human Papilloma Viruses from the Vagina: Use of a Dual Swab to Avoid Sampling Errors when Comparing Novel Flocked Swabs with Conventional Rayon Swabs.

Objectives

Several studies have shown equal sensitivity and specificity for vaginal swabs compared to endocervical swabs and first voided urine for the detection of sexually transmitted viruses and bacteria, like human papillomaviruses (HPV) and Chlamydia trachomatis (Ct). The easy way of taking samples opens the possibility for patients self-swabbing and self-testing. Even more the novel flocked swabs promise higher sensitivity compared to conventional swabs. We compared the detection rates of HPV and Ct from vaginal swabs by using a special dual swab.

Methods

Actually 326 asymptomatic patients where tested from vaginal dual swabs taken by the gynecologist during routine visits. The dual swab consisted of a normal rayon swab and a novel flocked nylon swab. After the sample was taken, the swabs were separated and each one was transferred in an individual dry tube for transportation to the laboratory. There 1 ml of 0.9% sodium chloride was added to the tubes before extraction for Polymerase Chain Reaction (PCR). Extraction was done from 0.5 ml, 0.5 ml was stored frozen. Detection of HPV high risk types was done by the Digene® HPV Test*, using Hybrid Capture® 2 (hc2) technology. Ct was detected by an in house real-time PCR on the Light-Cycler described earlier (Development and Validation of Fourteen LightCycler Real Time PCR Assays for the Quantification or Qualitative Detection of Common Viral and Bacterial Infections in Various Specimen Types. T. Krech, S. Chong, X. Song, T. Bruderer, D. Jang, J.B. Mahony, A.K. Petrich, K. Luinstra, S. Castriciano, M. Smieja, M. Chernesky)

Results

326 asymptomatic patients were tested for both Chlamydia trachomatis and Human papillomavirus with both swabs type. The flocked swabs detected 6 positive and 320 negative Ct, while the Rayon swabs detected 4 positive and 322 negative, missing 2 positive Ct. HPV detected 32 positive and 294 negative with the flocked swabs, while the Rayon swabs detected 17 positive and 305 negative. The flocked swabs detected 15 additional positive that were negative with the rayon swabs. The Ct positive rate was 1.84% with an average of 63 copies/ml for the flocked swabs and 1.2% with an average of 9 copies/ml for the Rayon swabs. The HPV positive rate for the flocked swabs was 9.81% and 5.21% for the Rayon swabs. Sampling with flocked swabs gave a 65.21% and 53.1% higher yield for Ct and HPV respectively.

Conclusion

Flocked swabs provide a higher sensitivity than conventional rayon swabs with regard to both positive patients and DNA-copy numbers. This might make flocked swabs useful not only for PCR - diagnosis of sexually transmitted diseases from health care professionals collected samples but also from patient self collected samples. This opens a wide range of self-testing applications (see also www.self-testing.com) that can be offered to everybody for prophylaxis and diagnosis of diseases.