High Diagnostic Value of a New Real-Time Pneumocystis PCR from Bronchoalveolar Lavage in a Real-Life Clinical Setting.
BACKGROUND
To diagnose Pneumocystis jirovecii pneumonia (PCP), PCR testing in bronchoalveolar lavage (BAL) fluid has recently become an alternative to immunofluorescence testing (IFT); however, its diagnostic accuracy is less clear.


OBJECTIVE
To analyze the diagnostic value of a new semiquantitative real-time PCR (RT-PCR) in BAL in a real-life clinical setting.


METHODS
Retrospective analysis of all RT-PCR results [semiquantitative: negative, weakly positive, and strongly positive; measured in cycle thresholds (Ct)] in BAL in the period between 2010 and 2014. The diagnosis of PCP was defined by clinical, radiological, and laboratory signs and by treatment initiation. Any positive PCR was compared with subsequent IFT.


RESULTS
Of 128 patient samples, 32 had PCP. There is a relevant correlation of high significance between positive PCR Ct and IFT (r = -0.7781, p < 0.001), which amounts to about 60% of the variance. Sensitivity, specificity, and positive predictive values (PPV) of any positive RT-PCR were 100, 80, and 63%, respectively. No patient with negative RT-PCR had PCP. Specificity and PPV are 100% in strongly positive RT-PCR, whereas they decrease to 80 and 21% in weakly positive RT-PCR.


CONCLUSIONS
A negative RT-PCR (Ct >45) rules out PCP. A strongly positive PCR (Ct <31.5) confirms PCP. In these cases, the diagnostic value of the new method is at least equal to the IFT. A weakly positive PCR probably represents pneumocystis colonization and can occur under PCP treatment.
Pneumologie, Infektiologie, Intensivmedizin, Medizinische Klinik Nord, Klinikum Dortmund gGmbH, Dortmund, Germany.
Markus
M
Unnewehr
Hendrik
H
Friederichs
Patricia
P
Bartsch
Bernhard
B
Schaaf
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry* / Q000382:microbiology; D004269:DNA, Bacterial / Q000032:analysis*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D025202:Molecular Diagnostic Techniques; D045363:Pneumocystis carinii / Q000235:genetics*; D011020:Pneumonia, Pneumocystis / Q000175:diagnosis*; D060888:Real-Time Polymerase Chain Reaction; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D055815:Young Adult
D004269:DNA, Bacterial