In Replay: Pneumocystis Pneumonia Following Rituximab

Abstract

To the EditorI thank Dr Farkas and colleagues for their interest in our study on the potential risks of developing Pneumocystis pneumonia (PcP) in patients with compromised immune systems receiving rituximab.1Martin-Garrido I Carmona EM Specks U Limper AH Pneumocystis pneumonia in patients treated with rituximab.Chest. 2013; 144: 258-265Abstract Full Text Full Text PDF PubMed Scopus (118) Google Scholar The letter raises the important question about whether the three patients reported in the case series might actually represent colonization rather than PcP. This question arose because the cases were detected by polymerase chain reaction (PCR) assay. We believe that these cases represent true PcP rather than colonization; thus, further clarification is needed.Many PCR assays reported in the literature amplify mitochondrial DNA sequences.2Ribes JA Limper AH Espy MJ Smith TF PCR detection of Pneumocystis carinii in bronchoalveolar lavage specimens: analysis of sensitivity and specificity.J Clin Microbiol. 1997; 35: 830-835PubMed Google Scholar Hence, they amplify multicopy Pneumocystis target genes, significantly heightening detection sensitivity. In addition, these assays often rely on nested PCR approaches where the initial amplification products are subsequently reamplified, yielding even greater sensitivity.3Krajicek BJ Thomas Jr, CF Limper AH Pneumocystis pneumonia: current concepts in pathogenesis, diagnosis, and treatment.Clin Chest Med. 2009; 30: 265-278Abstract Full Text Full Text PDF PubMed Scopus (57) Google Scholar Indeed, such approaches may be overly sensitive for many routine clinical applications. Accordingly, previously reported PCR assay approaches are known to detect Pneumocystis colonization in addition to invasive infections.4Morris A Sciurba FC Lebedeva IP et al.Association of chronic obstructive pulmonary disease severity and Pneumocystis colonization.Am J Respir Crit Care Med. 2004; 170: 408-413Crossref PubMed Scopus (174) Google Scholar However, the Pneumocystis PCR assay used in our clinical microbiology laboratory has unique features that circumvent many of these issues.5Wilson JW Limper AH Grys TE Karre T Wengenack NL Binnicker MJ Pneumocystis jirovecii testing by real-time polymerase chain reaction and direct examination among immunocompetent and immunosuppressed patient groups and correlation to disease specificity.Diagn Microbiol Infect Dis. 2011; 69: 145-152Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar To address the issues of colonization, we use a diagnostic Pneumocystis PCR assay that uses a single-copy target gene from Pneumocystis jirovecii, namely pjcdc2.5Wilson JW Limper AH Grys TE Karre T Wengenack NL Binnicker MJ Pneumocystis jirovecii testing by real-time polymerase chain reaction and direct examination among immunocompetent and immunosuppressed patient groups and correlation to disease specificity.Diagn Microbiol Infect Dis. 2011; 69: 145-152Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar We also perform quantitative amplification with real-time PCR and do not reamplify the reaction products with nested PCR.5Wilson JW Limper AH Grys TE Karre T Wengenack NL Binnicker MJ Pneumocystis jirovecii testing by real-time polymerase chain reaction and direct examination among immunocompetent and immunosuppressed patient groups and correlation to disease specificity.Diagn Microbiol Infect Dis. 2011; 69: 145-152Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar With this PCR assay, we have observed an increase (approximately 7%) in total diagnostic sensitivity over smeared stains alone. In addition, in now > 200 consecutive cases without clinical evidence of infection, we have not detected a PCR signal. Hence, the assay used in this study was specifically designed to detect PcP rather than colonization.5Wilson JW Limper AH Grys TE Karre T Wengenack NL Binnicker MJ Pneumocystis jirovecii testing by real-time polymerase chain reaction and direct examination among immunocompetent and immunosuppressed patient groups and correlation to disease specificity.Diagn Microbiol Infect Dis. 2011; 69: 145-152Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar On this basis, our laboratory now routinely uses this PCR assay rather than microscopic examination for the diagnosis of Pneumocystis infection. Moreover, it must be noted that the patients in the current report had active lung infiltration as well as signs and symptoms of infection. In each patient, there was no evidence of any other significant alternative organism, despite routine comprehensive culture, antigen detection, and molecular diagnostic assays performed to rigorously detect typical and atypical bacteria, viruses, and other fungi. Thus, in all three patients, the clinical evidence pointed to active PcP rather than to colonization. To the EditorI thank Dr Farkas and colleagues for their interest in our study on the potential risks of developing Pneumocystis pneumonia (PcP) in patients with compromised immune systems receiving rituximab.1Martin-Garrido I Carmona EM Specks U Limper AH Pneumocystis pneumonia in patients treated with rituximab.Chest. 2013; 144: 258-265Abstract Full Text Full Text PDF PubMed Scopus (118) Google Scholar The letter raises the important question about whether the three patients reported in the case series might actually represent colonization rather than PcP. This question arose because the cases were detected by polymerase chain reaction (PCR) assay. We believe that these cases represent true PcP rather than colonization; thus, further clarification is needed.Many PCR assays reported in the literature amplify mitochondrial DNA sequences.2Ribes JA Limper AH Espy MJ Smith TF PCR detection of Pneumocystis carinii in bronchoalveolar lavage specimens: analysis of sensitivity and specificity.J Clin Microbiol. 1997; 35: 830-835PubMed Google Scholar Hence, they amplify multicopy Pneumocystis target genes, significantly heightening detection sensitivity. In addition, these assays often rely on nested PCR approaches where the initial amplification products are subsequently reamplified, yielding even greater sensitivity.3Krajicek BJ Thomas Jr, CF Limper AH Pneumocystis pneumonia: current concepts in pathogenesis, diagnosis, and treatment.Clin Chest Med. 2009; 30: 265-278Abstract Full Text Full Text PDF PubMed Scopus (57) Google Scholar Indeed, such approaches may be overly sensitive for many routine clinical applications. Accordingly, previously reported PCR assay approaches are known to detect Pneumocystis colonization in addition to invasive infections.4Morris A Sciurba FC Lebedeva IP et al.Association of chronic obstructive pulmonary disease severity and Pneumocystis colonization.Am J Respir Crit Care Med. 2004; 170: 408-413Crossref PubMed Scopus (174) Google Scholar However, the Pneumocystis PCR assay used in our clinical microbiology laboratory has unique features that circumvent many of these issues.5Wilson JW Limper AH Grys TE Karre T Wengenack NL Binnicker MJ Pneumocystis jirovecii testing by real-time polymerase chain reaction and direct examination among immunocompetent and immunosuppressed patient groups and correlation to disease specificity.Diagn Microbiol Infect Dis. 2011; 69: 145-152Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar To address the issues of colonization, we use a diagnostic Pneumocystis PCR assay that uses a single-copy target gene from Pneumocystis jirovecii, namely pjcdc2.5Wilson JW Limper AH Grys TE Karre T Wengenack NL Binnicker MJ Pneumocystis jirovecii testing by real-time polymerase chain reaction and direct examination among immunocompetent and immunosuppressed patient groups and correlation to disease specificity.Diagn Microbiol Infect Dis. 2011; 69: 145-152Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar We also perform quantitative amplification with real-time PCR and do not reamplify the reaction products with nested PCR.5Wilson JW Limper AH Grys TE Karre T Wengenack NL Binnicker MJ Pneumocystis jirovecii testing by real-time polymerase chain reaction and direct examination among immunocompetent and immunosuppressed patient groups and correlation to disease specificity.Diagn Microbiol Infect Dis. 2011; 69: 145-152Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar With this PCR assay, we have observed an increase (approximately 7%) in total diagnostic sensitivity over smeared stains alone. In addition, in now > 200 consecutive cases without clinical evidence of infection, we have not detected a PCR signal. Hence, the assay used in this study was specifically designed to detect PcP rather than colonization.5Wilson JW Limper AH Grys TE Karre T Wengenack NL Binnicker MJ Pneumocystis jirovecii testing by real-time polymerase chain reaction and direct examination among immunocompetent and immunosuppressed patient groups and correlation to disease specificity.Diagn Microbiol Infect Dis. 2011; 69: 145-152Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar On this basis, our laboratory now routinely uses this PCR assay rather than microscopic examination for the diagnosis of Pneumocystis infection. Moreover, it must be noted that the patients in the current report had active lung infiltration as well as signs and symptoms of infection. In each patient, there was no evidence of any other significant alternative organism, despite routine comprehensive culture, antigen detection, and molecular diagnostic assays performed to rigorously detect typical and atypical bacteria, viruses, and other fungi. Thus, in all three patients, the clinical evidence pointed to active PcP rather than to colonization. I thank Dr Farkas and colleagues for their interest in our study on the potential risks of developing Pneumocystis pneumonia (PcP) in patients with compromised immune systems receiving rituximab.1Martin-Garrido I Carmona EM Specks U Limper AH Pneumocystis pneumonia in patients treated with rituximab.Chest. 2013; 144: 258-265Abstract Full Text Full Text PDF PubMed Scopus (118) Google Scholar The letter raises the important question about whether the three patients reported in the case series might actually represent colonization rather than PcP. This question arose because the cases were detected by polymerase chain reaction (PCR) assay. We believe that these cases represent true PcP rather than colonization; thus, further clarification is needed. Many PCR assays reported in the literature amplify mitochondrial DNA sequences.2Ribes JA Limper AH Espy MJ Smith TF PCR detection of Pneumocystis carinii in bronchoalveolar lavage specimens: analysis of sensitivity and specificity.J Clin Microbiol. 1997; 35: 830-835PubMed Google Scholar Hence, they amplify multicopy Pneumocystis target genes, significantly heightening detection sensitivity. In addition, these assays often rely on nested PCR approaches where the initial amplification products are subsequently reamplified, yielding even greater sensitivity.3Krajicek BJ Thomas Jr, CF Limper AH Pneumocystis pneumonia: current concepts in pathogenesis, diagnosis, and treatment.Clin Chest Med. 2009; 30: 265-278Abstract Full Text Full Text PDF PubMed Scopus (57) Google Scholar Indeed, such approaches may be overly sensitive for many routine clinical applications. Accordingly, previously reported PCR assay approaches are known to detect Pneumocystis colonization in addition to invasive infections.4Morris A Sciurba FC Lebedeva IP et al.Association of chronic obstructive pulmonary disease severity and Pneumocystis colonization.Am J Respir Crit Care Med. 2004; 170: 408-413Crossref PubMed Scopus (174) Google Scholar However, the Pneumocystis PCR assay used in our clinical microbiology laboratory has unique features that circumvent many of these issues.5Wilson JW Limper AH Grys TE Karre T Wengenack NL Binnicker MJ Pneumocystis jirovecii testing by real-time polymerase chain reaction and direct examination among immunocompetent and immunosuppressed patient groups and correlation to disease specificity.Diagn Microbiol Infect Dis. 2011; 69: 145-152Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar To address the issues of colonization, we use a diagnostic Pneumocystis PCR assay that uses a single-copy target gene from Pneumocystis jirovecii, namely pjcdc2.5Wilson JW Limper AH Grys TE Karre T Wengenack NL Binnicker MJ Pneumocystis jirovecii testing by real-time polymerase chain reaction and direct examination among immunocompetent and immunosuppressed patient groups and correlation to disease specificity.Diagn Microbiol Infect Dis. 2011; 69: 145-152Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar We also perform quantitative amplification with real-time PCR and do not reamplify the reaction products with nested PCR.5Wilson JW Limper AH Grys TE Karre T Wengenack NL Binnicker MJ Pneumocystis jirovecii testing by real-time polymerase chain reaction and direct examination among immunocompetent and immunosuppressed patient groups and correlation to disease specificity.Diagn Microbiol Infect Dis. 2011; 69: 145-152Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar With this PCR assay, we have observed an increase (approximately 7%) in total diagnostic sensitivity over smeared stains alone. In addition, in now > 200 consecutive cases without clinical evidence of infection, we have not detected a PCR signal. Hence, the assay used in this study was specifically designed to detect PcP rather than colonization.5Wilson JW Limper AH Grys TE Karre T Wengenack NL Binnicker MJ Pneumocystis jirovecii testing by real-time polymerase chain reaction and direct examination among immunocompetent and immunosuppressed patient groups and correlation to disease specificity.Diagn Microbiol Infect Dis. 2011; 69: 145-152Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar On this basis, our laboratory now routinely uses this PCR assay rather than microscopic examination for the diagnosis of Pneumocystis infection. Moreover, it must be noted that the patients in the current report had active lung infiltration as well as signs and symptoms of infection. In each patient, there was no evidence of any other significant alternative organism, despite routine comprehensive culture, antigen detection, and molecular diagnostic assays performed to rigorously detect typical and atypical bacteria, viruses, and other fungi. Thus, in all three patients, the clinical evidence pointed to active PcP rather than to colonization. Pneumocystis Pneumonia Following RituximabCHESTVol. 145Issue 3PreviewWe read with interest the article by Martin-Garrido et al1 in a recent issue of CHEST (July 2013) that described a series of 30 cases of Pneumocystis pneumonia at the Mayo Clinic between 1998 and 2011 in association with rituximab. Three cases within this series were associated solely with rituximab (with the remaining 27 cases also associated with steroids, chemotherapy, or both, which are known risk factors). It is noteworthy that in all three cases, the diagnosis was made solely on the basis of polymerase chain reaction (PCR) testing compared with only 12 of the remaining 27 cases. Full-Text PDF