The diagnosis can be confirmed by the characteristic appearance of the chest X-ray and an arterial oxygen level (PaO2) that is strikingly lower than would be expected from symptoms. Gallium 67 scans are also useful in the diagnosis. They are abnormal in about 90% of cases and are often positive before the chest X-ray becomes abnormal. Chest X-ray typically shows widespread pulmonary infiltrates. CT scan may show pulmonary cysts (not to be confused with the cyst-forms of the pathogen). File:PCPxray.Chest X-ray of increased opacification (whiteness) in the lower lungs. File:X-ray of ground glass opacities of<unk> .These chest radiographs are of two patients. Both show ground glass opacities. The left X-ray shows a much more subtle ground-glass appearance while the right X-ray shows a much more gross ground-glass appearance mimicking pulmonary edema. File:X-ray of cyst in<unk>  1.X-ray of a cyst in<unk>  File:HRCT of mosaic ground-glass opacities of<unk>  2.High-resolution computed tomography (HRCT) showing ground-glass attenuation with a geographic or mosaic distribution. File:HRCT of cysts of<unk> .HRCT of cysts of<unk> . These are usually multiple and bilateral, but range in size, shape and distribution. The diagnosis can be definitively confirmed by histological identification of the causative organism in sputum or bronchoalveolar lavage (lung rinse). Staining with toluidine blue, silver stain, periodic acid-Schiff stain, or an immunofluorescence assay shows the characteristic cysts. The cysts resemble crushed ping-pong balls and are present in aggregates of two to eight (and not to be confused with Histoplasma or Cryptococcus, which typically do not form aggregates of spores or cells). A lung biopsy would show thickened alveolar septa with fluffy eosinophilic exudate in the alveoli. Both the thickened septa and the fluffy exudate contribute to dysfunctional diffusion capacity that is characteristic of this pneumonia.<unk>  infection can also be diagnosed by immunofluorescent or histochemical staining of the specimen, and more recently by molecular analysis of polymerase chain reaction products comparing DNA samples. Notably, simple molecular detection of P. jirovecii in lung fluids does not mean that a person has<unk>  or infection by HIV. The fungus appears to be present in healthy individuals in the general population. A blood test to detect β-D-glucan (a part of the cell wall of many different types of fungi) can also help in the diagnosis of<unk> .
Pneumocystis pneumonia
Pneumonia alba
Tuberculosis
Allergic bronchopulmonary aspergillosis
Histoplasmosis
Fungal pneumonia
Aspergillosis
Primary pulmonary coccidioidomycosis