title: Real-time PCR is more specific than conventional PCR for induced sputum diagnosis of Pneumocystis pneumonia in immunocompromised patients without HIV infection.
abstract: OBJECTIVE
  The diagnosis of Pneumocystis pneumonia (PCP) is based on microscopic examination of respiratory specimens. PCP patients without AIDS have a lower burden of P. jiroveci than those with AIDS, which leads to difficulty in detecting the organisms. Although conventional PCR (c-PCR) has been used to detect the DNA, it is frequently positive in patients with colonization. Real-time PCR (r-PCR), a method to detect the DNA quantitatively, might be helpful in distinguishing between infection and colonization. We investigated the utility of real-time PCR in the diagnosis of PCP in non-AIDS patients.
  
  
  METHODS
  Induced sputum samples obtained from 86 non-HIV immunocompromized patients with clinical symptoms of pulmonary infection were evaluated for the presence of Pneumocystis jiroveci-specific DNA using c-PCR and r-PCR. The diagnosis of PCP was confirmed by typical clinical and radiological findings and response to treatment.
  
  
  RESULTS
  Of the 86 patients, 17 were diagnosed as having PCP. Twenty-eight samples were positive for c-PCR, but the false-positive rate was high (46.4%). Sensitivity, specificity and positive predictive values (PPV) of c-PCR were 88.2%, 81.2% and 53.6%, respectively. Concentrations of the DNA detected by r-PCR were significantly higher in PCP patients than in non-PCP patients. Using 30 copies per tube as a cut-off value for the diagnosis of PCP, the sensitivity (82.4%) of r-PCR was almost equal to c-PCR. Notably, its specificity and PPV were higher than c-PCR (98.6% and 93.3%, respectively).
  
  
  CONCLUSIONS
  r-PCR on induced sputum is more useful for diagnosing PCP than c-PCR in non-HIV immunocompromized patients, especially in terms of distinguishing between colonization and infection.
authors.affiliation: Second Division, Department of Internal Medicine, Hamamatsu University School of Medicine, Hamamatsu, Shizuoka, Japan.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Fujisawa
authors.forename: Takafumi
authors.initials: T
authors.lastname: Suda
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Matsuda
authors.forename: Naoki
authors.initials: N
authors.lastname: Inui
authors.forename: Yutaro
authors.initials: Y
authors.lastname: Nakamura
authors.forename: Jun
authors.initials: J
authors.lastname: Sato
authors.forename: Mikio
authors.initials: M
authors.lastname: Toyoshima
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Nakano
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Yasuda
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Gemma
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hayakawa
authors.forename: Kingo
authors.initials: K
authors.lastname: Chida
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004271:DNA, Fungal / Q000032:analysis / Q000235:genetics; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D016867:Immunocompromised Host / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D045363:Pneumocystis carinii / Q000235:genetics*; D011020:Pneumonia, Pneumocystis / Q000175:diagnosis* / Q000276:immunology*; D016133:Polymerase Chain Reaction / Q000379:methods*; D012680:Sensitivity and Specificity; D013183:Sputum / Q000382:microbiology*
chemical_list: D004271:DNA, Fungal