<prompt> The definitive diagnosis of Pneumocystis carinii pneumonia is -Serological testChest X-rayFinding cysts in tissue specimensCT scan of thorax  <response>: Its life cycle begins when cysts rupture and release sporozoites, which mature into trophozoites that eventually form cysts. The diagnostic methods for P. carinii pneumonia PCP have progressed from open lung biopsy to bronchoalveolar lavage BAL and induced sputum analysis . Ref Harrison20th edition pg 1056 