TY - JOUR T1 - <em>From the authors</em> JF - European Respiratory Journal JO - Eur Respir J SP - 392 LP - 394 DO - 10.1183/09031936.04.00135404 VL - 25 IS - 2 AU - G. L. Biscione AU - J. Corne AU - A. J. Chauhan AU - S. L. Johnston Y1 - 2005/02/01 UR - http://erj.ersjournals.com/content/25/2/392.2.abstract N2 - We thank D.L. Hahn for his interest in our study 1 and for commenting upon the interesting issues he raised relating to the study and its interpretation, particularly regarding the presence of acute infection, reactivation, colonisation or chronic infection. These are important issues and informed debate about them is to be welcomed. D.L. Hahn comments that, in the introduction, we stated that Chlamydophila pneumoniae serology could not differentiate acute from other infections. In fact, we stated that serology cannot reliably differentiate between past and present infection, or acute and chronic infection. We acknowledge that there are published proposed serological criteria for acute primary infection using the microimmunofluorescence (MIF) test 2. However, these authors stated that “standardized definitions for ‘acute infection’ and ‘past exposure’ are proposed”, and that “these standards should be applied in future investigations and periodically modified as indicated”. Although certainly the best advice available to date, we believe that these excellent recommendations are certainly not the last word in C. pneumoniae diagnosis, which remains a very much still evolving field. As D.L. Hahn states, we also implied that C. pneumoniae serology may be (not “was”) nonspecific, i.e. cross-reactive with other Chlamydia species 1. We stand by this comment, as there is data indicating this may be the … ER -