Table 2– Results of the diagnostic procedure according to the performance of the currently recommended standard diagnostic approach with immunofluorescence (IF) as first test

First test	Second test	Results
IF	PCR	Total subjects	Definitive PCP (IF test positive)	Possible PCP	PCP excluded
Positive	Positive	71 (100)	71 (100)	0	0
	Negative	0	0
Negative	Positive	18 (10.5)	0	3 (16.6)	15 (83.3)
	Negative	153 (89.5)	0	1 (0.65)^#	152 (99.3)

Data are presented as n (%). PCP: Pneumocystitis pneumonia.^#: PCP could not be formally ruled out in only one patient with rheumatoid arthritis and lung involvement. The treating physicians prescribed 3-week therapy against Pneumocystis jirovecii, but judged the acute lung disease as “more likely to be caused by autoimmune disease exacerbation rather than PCP” in the discharge letter. Retrospective reviewers unaware of the PCR result agreed with this interpretation.