Ethics approval and consent to participate
The study was approved by the Ethics Commission of the Hamburg Medical Association on 12 August 2013 (file number PV 4535). All study participants gave their written informed consent prior to their participation in the study.
Consent for publication
All participants gave their written consent to publish their names in the ‘Acknowledgements’ section.
Availability of data and material
The datasets analysed during the current study are not publicly available as data sharing with other researchers was not part of patients’ informed consent.
Competing interests
The authors declare that they have no competing interests.
Funding
The study was supported by the Hamburg and Schleswig-Holstein Association of Statutory Health Insurance Physicians. The funding body had no role in the design of the study and collection, analysis, and interpretation of data and in writing the manuscript.
Authors' contributions
MS, IS and HH conceived and designed the study. DL, HOW, TR and AK significantly contributed to the study design and/or discussion of the study results. IS analysed the data. IS and HH drafted the manuscript. All the authors commented on the draft and read and approved the final version of the manuscript.
Acknowledgements
We would like to express our appreciation to the numerous GPs who facilitated this study with their participation, namely: Karl-Heinz Aeffner, Volker Ahrens, Susanne Assmus, Ayhan Ayikli, Aina Barbakow, Hellmut Baur, Nina Becker, Gunter Behrend, Sven Behrens, Daisy Benson, Ulrich Berghof, Friederike Besch, Jürgen Biesewig-Siebenmorgen, Claudia Bleil, Karen Blumenbach, Eckart Boehnke, Ulrike Börgerding, Hans Böttcher, Marcus Brand, Jens Bräuer, Nicolay Breyer, Broder Brodersen, Peter Brümmer, Paola Brusa Düwel, Christian Butt, Kerstin Dann, Natascha Dannheisser, Susanne Dennig, Christian Dettmann, Björn-Ole Dieckvoß, Frank Döhling, Markus Dohrmann, Gero Domzig, Sabine Drengenberg, Thomas Drescher, Norbert Eckhardt, Henning Eggers, Jürgen Elis, Heike Elsen, Michael Emken, Susanne Faas-Ramm, Heino Feldbrügge, Matthias Fischer, Thomas Flasinski, Christiane Fock, Kurt Forstreuter, Dorothea Frederking, Dierk Freundl, Clemens Frey, Frank Fueting, Inka Führer, Michael Funke, Ralf Gade, Jan Geldmacher, Birgit Gier-Moser, Dagmar Gottkehaskamp, Daniel Graf, Inga Grimm, Carmen Cecilia Groninga, Peter Gründahl, Christine Gschwend, Nils Hansen, Henning Harder, Regina Hartwig-Haars, Ruth Hauck, Rudolf Hauschildt, Jürgen Hausmann, Henrik Heinrichs, Beate Heitmann, Rainer Hennecke, Franz Herrschel, Wolfgang Herzog, Corinna Hess, Ulrike Heye, Pamela Hilgenberg, Bernd Hinz, Andreas Hofinga, Herbert Hofstetter, Karl Heinz Houcken, Charlotte Hübner-Urch, Peter Humbert, JanaHusemann, Claus Jaeckel, Markus Jäger-Rosiny, Heinz Jarmatz, Claudia Kahle, Lars Kämpfer, Stefan Kasischke, Dieter Kayser, Carlos Keller, Christiane Kindler-Behrens, Bernd Klemeyer, Michael Klemperer, Hans-Peter Knapp, Martina Koch, Dorothea Koersten, Stefan Köhn, Martin Kohne, Daniel Körbacher, Thomas Kötter, Toni Koudmani, Stefan Kreszis, Ute Lang, Raimund Leineweber, Nicole Lenzi-Sommer, Andreas Lindrum, Andrea Linsel, Thomas Loeseken, Daniel Lohmann, Margret Lorenzen, Berit Löwnau, Elisabeth Lübbers-Klare, Mirko Magens, Claudia Malchartzeck, Helmut Marczinkowski, Frank Meisel, Anne Meister, Albrecht Meister, Dagmar Menche, Wolf-Dieter Mengert, Hans-Georg Merkel, Ingo Migule, Andreas Mittelstädt, Eckart Möbius, Frank Möller, Rio Morawe, Mike Müller- Glamann, Karl-Christian Münter, Anila Nasery, Klaus-Peter Neizel-Tönnies, Marcus Netzel, Jonas Niemann, Birgit Obermeier, Michael Odinius, Swantje Ohlen, Ilse Ordemann, Irina Osinski, Christiane Otto, August Palatsik, Werner Petersen, Jürgen Pohl, Claudia Polay-Hehn, Uwe Pönnighaus, Dirk Rappenberg, Dirk Reese, Karin Rehder, Rainer Reiß, Friedel Rennekamp, Marlies Richter-Boehnke, Thomas Rohlfing, Ulrich Rose, Detlef Roshop, Anja Roß, Beatrice Roßbach, Janet Rossmann, Wolfgang Rumpf, Jörg Runge, Gerd Ruß, Detlef Schäfer, Peter-Andreas Schaper, Hans-Georg Schoermer, Manfred Schopf, Uta Schramm, Udo Schröder, Simon-Vitus Schuknecht, Walter Schulz, Susann Schütt, Jörg Schwarzkopf, Louis Sellier, Olaf Settgast, Helena Simov, Carsten Sommerfeld, Bettina Sponheim-Rambow, Maren Stadtlander-Rahm, Manfred Steinkohl, Andrea Stendel, Elke Sterling, Hans-Heiner Stöver, Ulrike Streit, Stefan Strzelec, Thomas Szlagowski, Georg Tacke, Gerrit Tarrach, Arjen Teetzmann, Silke Theisen, Jens Thomä, Bernd Thormählen, Sevine Tokdemir, Michael Topp, Matthias Trenkler, Thomas Tschirner, Christian Vahle, Martin Richard Vietor, Martina Vogler, Volker Voß, Meike Wagner, Jens Wagner, Doris Waller, Thomas Wasielewski, Jan Philip Wegner, Katrin Welke, Matthias Will, Sven-Ullrich Winter, Henning Winter, Delia Wirth, Lutz Witte, Anja Wittke, Thomas Wittke, Klaus Wogawa, Siegmar Zedler, Alexandra Zeidler, Eckhard Zeigert, Martin Zingel, Matthias Zink, Constantin Zoras and Nicole Zühlke.