Comparing Polymerase Chain Reaction Testing of Nasopharyngeal Swab and Lower Respiratory Tract Specimens for the Diagnosis of Pneumocystis jirovecii Pneumonia by Chew, R, Tozer, S, Ulett, K, Paterson, DL, Whiley, D, Sloots, T, Fielding, D, Zappala, C, Bashirzadeh, F, Hundloe, J, Bletchley, C, Woods, ML