This was an observational prospective study of consecutive patients with acute exacerbation of asthma admitted to the Emergency Room of Fondazione IRCCS Ospedale Maggiore Policlinico, Mangiagalli e Regina Elena Hospital, Milan, Italy, between January 2004 and December 2004. Acute exacerbation of bronchial asthma (AEBA) was defined as following: episodes of rapidly progressive increase in shortness of breath, cough, wheezing, or chest tightness, or some combination of these symptoms necessitating a non-scheduled visit, and associated to a decrease of respiratory airflow quantified by measurements of peak expiratory flow (PEF) or FEV1 . Severe exacerbation of asthma was defined when PEF on admission was <50% according to BTS criteria . We chose the PEF value measurement as the only criterion for acute severe asthma exacerbation in Emergcency Room since it is a direct and reproducible measurement easily controlled in the follow-up.
Subjects satisfying criteria for acute exacerbation of asthma were eligible for the study if all the following inclusion criteria were fulfilled: 1) age > 18 yrs; 2) history of typical bronchial asthma > 6 mo and 3) smoking history < 10 pack/yrs.
Patients with a radiological diagnosis of pneumonia or with impaired consciousness on admission were excluded from the study.
On admission, past medical history and active medications were collected; every patient underwent the following examinations: PEF measurements (best out of three), spirometry, an oropharyngeal swab specimens and a blood sample for serologic testing.
Patients were treated according to British Thoracic Society guidelines, considering the degree of severity . In particular, patients presenting with a severe acute attack were treated with systemic steroids, whereas those with a non-severe attack were treated with topic steroids.
Follow-up was performed at 2–4 days (Visit 1), at 10–14 days (Visit 2), and at 4–8 weeks (Visit 3), including functional evaluation by spirometry. A second blood sample was drawn for serologic testing (convalescence phase) 4–8 weeks after the admission.
Serologic tests included IgG and IgM for C. pneumoniae (microimmunofluorescence test, Labsystems, Helsinki, Finland), and IgG and IgM for M. pneumoniae (ELISA test, Pantec, Turin, Italy). On oropharyngeal swab specimens a nested-polymerase chain reaction (PCR) technique for the detection of C. pneumoniae DNA  was performed.
Acute C. pneumoniae infection was defined as IgM titre ≥ 1:16 or a fourfold increase in the specific IgG . Acute M. pneumoniae infection was defined as IgM titre ≥ 1:16 or a fourfold increase in the specific IgG . The person performing the MIF test was blinded to the patient diagnosis and characteristics.
Patients were divided into two groups according to the presence or the absence of acute Chlamydia and/or Mycoplasma pneumoniae infection (AAI). The two groups were compared according to the degree of functional impairment.
A sub-analysis was performed among the group of patients with acute atypical infection in order to evaluate the degree of functional impairment between the two different pathogens.
Local IRB review was performed and informed consent was obtained from all patients on admission to the study.
All data were statistically analyzed with SPSS version 10.1 (Chicago, Il). A descriptive statistics at baseline with continuous data expressed as a mean or median (depending on distribution) ± SD was performed, and data were compared between the group with AAI and the group without AAI using ANOVA test. Baseline categorical data between the two groups were compared by the χ2 test or Fisher's exact test when appropriate. p value < 0.05 was considered statistically significant. Among the group with AAI, the same test was applied to compare continuous data between the group with acute C. pneumoniae infection and the group with acute M. pneumoniae infection.