Newly diagnosed HIV infection with advanced disease (CD4 count <200)

Patients with previous PCP or CD4 count <200 who are not taking prophylaxis

Subacute onset

Fever (∼90%)

Cough (∼95%), usually non-productive Progressive breathlessness (∼95%) Tachypnoea (∼60%)

Chest examination normal in ∼50%

Initially normal in up to 25%

Commonest abnormalities are diffuse bilateral interstitial or alveolar shadowing

Lobar consolidation rare. Pleural effusion rare. Pneumothorax may occur

Staining of induced sputum for P. jirovecii trophic forms and cysts

Specificity ∼100%, sensitivity 50–90%

PCR Sensitivity 98%, specificity 80–98%

Indicated if PCP is suspected but induced sputum is non-diagnostic or cannot be done

Specificity ∼100%, sensitivity ∼80–90%

First choice: co-trimoxazole PO or IV for 21 days. Causes haemolysis in glucose-6-phosphate dehydrogenase-deficient patients (African/Mediterranean). Other side effects include nausea, vomiting, fever, rash, marrow suppression and raised transaminases.

Alternative regimens: primaquine + clindamycin; atovaquone; pentamidine

Start immediately if severe PCP (breathless at rest; PaO2 breathing air <8 kPa; extensive interstitial shadowing on chest X-ray)

Give prednisolone 40 mg twice daily PO for 5 days, followed by prednisolone 40 mg daily PO for 5 days, then prednisolone 20 mg daily PO for 11 days