Comparison of different methods to diagnose pneumocystis jiroveci pneumonia in children with haematological malignancies

Giemsa stain and PCR [single and nested PCR] were compared to a direct immunofluorescence assay [IFA] for the detection of Pneumocystis jiroveci in immuno-compromised patients with haematological malignancies, suspected of having P. jiroveci pneumonia. A total of 50 specimens [3 bronchoalveolar lavages [BAL], 16 sputum samples and 31 nasopharyngeal aspirate samples] were obtained from the Paediatric Oncology Unit of Kasr El-Aini Oncology Centre, Faculty of Medicine, Cairo University. Direct immunofluorescence [the gold standard] could detect 4 positive cases. Giemsa stain could only detect one positive case, being 25% sensitive and 100% specific. Single PCR could detect 3 positive cases, being 75% sensitive and 100% specific. Nested PCR could detect 36 positive cases, being 100% sensitive and 19.2% specific. We conclude that whenever possible, BAL samples should be obtained, for the diagnosis of P. jiroveci pneumonia [PJP]. Diagnosis of PJP should best be performed by IF or single PCR, especially if non-invasive samples are used. Nested PCR is recommended for detection of P. jiroveci in all immunosuppressed asymptomatic patients to identify a group of patients at high risk of developing PJP in the future, for whom proper chemoprophylaxis against P. jiroveci may be beneficial