Objective: Pneumocystis jirovecii pneumonia (PCP) is one of the most important life-threatening diseases in immunocompromised patients having an underlying disease or using immunosuppressive drugs including steroids. Pneumocystis jirovecii, previously known as a protozoan and now accepted as a fungus, is the causative agent of PCP. The purpose of the study is to evaluate data by determining the frequency of patients with P. jirovecii diagnosed by direct fluorescent antibody (DFA) method among children and adults admitted to our hospital with suspected PCP.

Materials and Methods: Two hundred and fifty-five respiratory samples sent to parasitology laboratory between 2003 and 2011 were included in the study. Samples were processed by using direct immunofluorescence technique with MeriFluor Pneumocystis (MeridianBioscience, USA) commercial kit which uses specific monoclonal antibodies against cell wall and matrix antigens of human P. jirovecii cyst, sporozoite and trophozoite in accordance with the recommendations of the manufacturer.

Results: Most of the samples came from the clinics of internal medicine, infectious diseases and chest diseases. Of 255 patients included in the study, 152 (60%) were male, 103 (40%) were female and the mean age was 46.7 years. Of the 255 samples, 138 (54%) were positive and 117 (46%) were negative. Of the positive patients, 79 (57%) were male, 59 (43%) were female and 14 (10%) were under the age of 18. The most frequently seen disease in P. jirovecii positive patients was haematologic maligancy which was seen in 75 patients (54.3%).

Conclusions: Patients with Acquired immune deficiency syndrome (AIDS) and haematologic disorders were the most affected groups by PCP. The most commonly used immunologic technique in the diagnosis of PCP is immunofluorescence. We suggest that the frequency of P. jirovecii shouldn't be overlooked in patients in the risk group and DFA can be preferred as the diagnostic tool for reducing mortality and morbidity due to its high sensitivity.