Nevertheless, conventional diagnostic methods are often insufficient for etiological diagnosis, and in half of these cases the causative pathogen cannot be determined. The use of multiplex polymerase
chain reaction (PCR), which is reported to be a reliable molecular method for diagnosing lower respiratory tract infections, has been used increasingly in recent years. The prominent advantage of PCR
method compared to culture is that, since PCR is based on replicating the DNA or RNA of very small
amount of microorganisms, it does not require living organisms and therefore is not affected by
the prior use of antibiotics. In addition, PCR is more sensitive for detection of multiple microorganisms
and delivers fast results