Chlamydia pneumonia is caused by Chlamydia pneumoniae infection. Chlamydia pneumoniae antibodies are subdivided into Chlamydia IgM antibodies and IgG antibodies. A positive IgG antibody to Chlamydia pneumoniae can determine whether the patient may have been infected with Chlamydia at some time in the past, specifically during the acute infection period, in combination with the IgM results. If the IgM is also positive, the patient is currently in a time of infection and needs to be given aggressive anti-inflammatory treatment if clinical symptoms are present. If the patient does not have any symptoms and the IgM antibody result is negative, it does not indicate that the patient is in the acute infection stage and can heal on his own without the use of drugs. Therefore, a positive IgG antibody cannot determine whether the patient is infected with Chlamydia, but more critically, the IgM antibody status.