Correspondence
Community-Acquired Pneumonia
N Engl J Med 1996; 334:861-863March 28, 1996
- Article
To the Editor:
We commend Drs. Bartlett and Mundy on their review of community-acquired pneumonia (Dec. 14 issue).1 Having served as a chair or member of the Canadian and American Thoracic Society (ATS) consensus committees that developed guidelines for the treatment of community-acquired pneumonia, we would like to address the differences between the approaches to initial empirical antibiotic therapy recommended by the British Thoracic Society (BTS) and by the Canadian and ATS consensus committees.2,3
The BTS statement dealt only with hospitalized patients with community-acquired pneumonia, whereas the Canadian and ATS statements dealt with both inpatients and outpatients. The BTS statement emphasized the importance of Streptococcus pneumoniae, while downplaying the importance of Mycoplasma pneumoniae, Legionella pneumophila, and gram-negative rods. The recommendations, however, were based in part on data from studies in which the definition of pneumonia was nonselective, sputum samples were not screened, and patients at risk for infection with gram-negative rods were essentially excluded. The BTS statement distinguished between pneumococcal pneumonia and “pneumonia of unknown etiology without features indicating severe or nonpneumococcal disease.” In contrast, the Canadian and ATS statements stressed that clinical features do not necessarily predict the microbial cause. This view is supported by data clearly showing that the history, physical examination, chest radiograph, and laboratory tests do not reliably predict the microbial cause.4
Drs. Bartlett and Mundy emphasize the need to identify the etiologic pathogen by Gram's staining and culture of sputum, plus selected serologic tests. The Canadian and ATS recommendations were less aggressive because of problems with the sensitivity and specificity of these tests and the lack of published data supporting their value. Although empirical therapy may be intellectually unappealing, studies of severe community-acquired pneumonia have shown that early appropriate (empirical) therapy directed at the likely pathogens can improve the outcome, whereas identification of the pathogen is not associated with improved survival rates.5,6 We are not opposed to appropriate diagnostic testing but would reserve it for suspected cases of infection with unusual or resistant pathogens or for infections that do not respond to initial empirical therapy.
Drs. Bartlett and Mundy identify areas for future study. No guidelines should be accepted without attempts to validate their usefulness in terms of outcomes.
6 ReferencesLionel A. Mandell, M.D.
McMaster University, Hamilton, ON L8V 1C3, CanadaMichael S. Niederman, M.D.
Winthrop–University Hospital, Mineola, NY 115011
Bartlett JG ,Mundy LM . Community-acquired pneumonia. N Engl J Med 1995;333:1618-1624
Full Text | Web of Science | Medline2
Mandell LA, Niederman M, Canadian Community Acquired Pneumonia Consensus Conference Group 3
Niederman MS ,Bass JB Jr ,Campbell GD , et al. Guidelines for the initial management of adults with community-acquired pneumonia: diagnosis, assessment of severity, and initial antimicrobial therapy. Am Rev Respir Dis 1993;148:1418-1426
Web of Science | Medline4
Fang GD ,Fine M ,Orloff J , et al. New and emerging etiologies for community-acquired pneumonia with implications for therapy: a prospective multicenter study of 359 cases. Medicine (Baltimore) 1990;69:307-316
Web of Science | Medline5
Leroy O ,Santre C ,Beuscart C , et al. A five-year study of severe community-acquired pneumonia with emphasis on prognosis in patients admitted to an intensive care unit. Intensive Care Med 1995;21:24-31
CrossRef | Web of Science | Medline6
Moine P, Vercken J-B, Chevret S, Chastang C, Gajdos P, French Study Group for Community-Acquired Pneumonia in the Intensive Care Unit
CrossRef | Web of Science | Medline
To the Editor:
Bartlett and Mundy mention only briefly the techniques for detecting pneumococcal capsular polysaccharides in sputum. We believe it is essential to perform tests for pneumococcal capsular polysaccharide antigen or pneumococcal cell-wall antigen in patients with community-acquired pneumonia, since these tests may establish the cause of the infection. Approximately half the cases of infection otherwise classified as pneumonia of unknown cause can be diagnosed as pneumococcal pneumonia when tests for capsular polysaccharide antigen are performed systematically on specimens of sputum or pleural fluid.1,2 Commercial diagnostic tests, such as latex agglutination or coagglutination, yield results in less than one hour and are easy to perform and inexpensive. Detection of antigen in sputum has the highest sensitivity and specificity (about 90 percent), is unaffected by prior use of antibiotics, and is therefore especially useful when cultures prove negative.
Two arguments have been made against this approach. One argument is that there may be false positive results because of oral α-hemolytic streptococci that cross-react in antigen-detection tests, and because of carriers of S. pneumoniae in the oropharynx. Two recent studies demonstrated that these factors are probably not a cause for concern.3,4 The other argument is that in patients with chronic bronchitis, the lower airways may be colonized with pneumococci in the absence of an acute infection of the lower respiratory tract. However, 106 to 107 pneumococci per milliliter are required for capsular antigen to be detectable in the latex-agglutination test.5 There is no evidence that antigen present in sputum is detected more often in patients with chronic bronchitis and community-acquired pneumonia than in those without chronic bronchitis.1
In our opinion, tests for pneumococcal antigen in sputum and pleural fluid are indispensable when Gram's staining of sputum samples yields inconclusive results or when patients have been pretreated with antibiotics. Because the results of the tests can be obtained so rapidly, treatment can be directed against S. pneumoniae.
5 ReferencesWim G. Boersma, M.D., Ph.D.
Medical Center Alkmaar, 1800 AM Alkmaar, the NetherlandsYvette Holloway, M.A.
Regional Public Health Laboratory, 9721 SW Groningen, the Netherlands1
British Thoracic Society, Public Health Laboratory Service
Web of Science | Medline2
Boersma WG ,Lowenberg A ,Holloway Y ,Kuttschrutter H ,Snijder JA ,Koeter GH . Pneumococcal capsular antigen detection and pneumococcal serology in patients with community acquired pneumonia. Thorax 1991;46:902-906
CrossRef | Web of Science | Medline3
Venkatesan P ,Sole K ,Tang C ,Macfarlane JT ,Finch RG . Oropharyngeal production of pneumococcal capsular antigen and the potential for contamination of expectorated sputum samples in pneumococcal pneumonia. Epidemiol Infect 1993;110:621-631
CrossRef | Web of Science | Medline4
Boersma WG ,Lowenberg A ,Holloway Y ,Kuttschrutter H ,Snijder JA ,Koeter H . The role of antigen detection in pneumococcal carriers: a comparison between cultures and capsular antigen detection in upper respiratory tract secretions. Scand J Infect Dis 1993;25:51-56
Web of Science | Medline5
Holloway Y ,Boersma WG ,Kuttschrutter H ,Snijder JA . Minimum number of pneumococci required for capsular antigen to be detectable by latex agglutination. J Clin Microbiol 1992;30:517-519
Web of Science | Medline
To the Editor:
Drs. Bartlett and Mundy provide an excellent review of the management of community-acquired pneumonia. In an era of substantial financial pressure, however, a more empirical, outcome-oriented approach to management may have advantages over one that focuses on the definitive identification of the microbial cause. Many common clinical beliefs and practices in the management of community-acquired pneumonia are not well supported by data.
First, although testing for legionella and mycoplasma may be important for epidemiologic surveillance, these tests have very low yields and rarely alter the management of the infection but do increase the cost of care. Indeed, many published guidelines for the diagnosis and treatment of community-acquired pneumonia do not recommend the routine use of these tests in hospitalized patients, as suggested in Table 1 of the article.1,2
Second, the recommendation that a hospitalized patient continue to receive parenteral therapy “until the patient has been afebrile for more than 24 hours,” although a clinical saw, is not based on solid evidence. This practice has been questioned by several investigators2,3 and abandoned by many clinicians (especially in the treatment of patients at low risk).
Finally, we agree that “few diseases are so characterized by disputes about diagnostic evaluation and therapeutic decisions.” The large variations in hospitalization rates, lengths of stay, and choice of antibiotics reflect the need for a more evidence-based approach to community-acquired pneumonia. Research has clearly identified many of the clinical and laboratory variables that predict mortality and morbidity from community-acquired pneumonia. This prognostic information has been summarized in at least one form, by the Pneumonia Severity Index, which has been extensively validated.4 The use of such prognostic tools to help make key clinical decisions should lead to more efficient yet effective care of patients with community-acquired pneumonia.
4 ReferencesEthan A. Halm, M.D.
Joshua P. Metlay, M.D., Ph.D.
Daniel E. Singer, M.D.
Massachusetts General Hospital, Boston, MA 02114Michael J. Fine, M.D.
University of Pittsburgh, Pittsburgh, PA 152131
Marrie TJ . Community-acquired pneumonia. Clin Infect Dis 1994;18:501-515
CrossRef | Web of Science | Medline2
Niederman MS ,Bass JB Jr ,Campbell GD , et al. Guidelines for the initial management of adults with community-acquired pneumonia: diagnosis, assessment of severity, and initial antimicrobial therapy. Am Rev Respir Dis 1993;148:1418-1426
Web of Science | Medline3
Sanders WE Jr ,Morris JF ,Alessi P , et al. Oral ofloxacin for the treatment of acute bacterial pneumonia: use of a nontraditional protocol to compare experimental therapy with “usual care“ in a multicenter clinical trial. Am J Med 1991;91:261-266
CrossRef | Web of Science | Medline4
Fine MJ ,Hanusa BH ,Lave JR , et al. Comparison of a disease-specific and a generic severity of illness measure for patients with community-acquired pneumonia. J Gen Intern Med 1995;10:359-368
CrossRef | Web of Science | Medline
Author/Editor Response
Dr. Bartlett replies:
To the Editor: The letters above nicely illustrate our point that “few diseases are so characterized by disputes about diagnostic evaluation and therapeutic decisions.”
Halm et al. argue that tests for legionella and mycoplasma should be restricted because of their cost and relatively low yield. Our review suggested that studies for legionella be performed in selected patients according to the relatively conservative recommendations of Edelstein,1 and we did not recommend studies for M. pneumoniae on the basis of our own experience. We agree that the practice of continuing parenteral therapy until the patient has been afebrile for more than 24 hours is not based on solid evidence. Clinical studies that address this issue are difficult to find. The only supporting study cited by the authors used oral ofloxacin for the entire course of treatment.
Drs. Mandell and Niederman also argue for more empiricism and less microbiology. Their recommendation is to reserve microbiologic studies for patients in whom infection with unusual or resistant pathogens is suspected, but this criterion might apply to most patients. S. pneumoniae is the most common identifiable pathogen in virtually all studies of community-acquired pneumonia and is clearly the most common cause of fatal cases of community-acquired pneumonia. A recent meta-analysis of 33,148 patients in 127 studies showed that S. pneumoniae accounted for 1019 of 1187 deaths (86 percent) among patients with an identifiable pathogen.2 Rates of resistance to penicillin are now commonly reported to be 15 to 30 percent and are increasing, and penicillin-resistant strains are often resistant to multiple antibiotics, making antibiotic selection difficult.3,4 The use of microbiologic studies only in patients who do not have a response is a flawed strategy, because fragile and common pathogens (S. pneumoniae and Haemophilus influenzae) usually cannot be recovered from any source after antibiotic treatment has been initiated.5
Dr. Boersma and Ms. Holloway argue in favor of more aggressive testing for S. pneumoniae with tests that detect capsular polysaccharide or the cell-wall antigen. We recommended this tactic with the use of Gram's staining and the quellung test on samples of expectorated sputum, which is the routine procedure at the microbiology laboratory of Johns Hopkins Hospital. As these authors point out, there is some concern about the specificity of the alternative antigen-detection methods they recommend, and these methods are used infrequently in most U.S. hospitals.
In our study of community-acquired pneumonia, a likely microbial pathogen was identified in 99 of 155 patients (64 percent) in whom pretreatment sputum studies were performed.6 The charge for Gram's staining and culture of expectorated secretions is $39, which is less than 1 percent of the median hospital bill of $4,500 for 400 patients with community-acquired pneumonia who were hospitalized at Johns Hopkins Hospital in 1993–1994. It will be difficult to convince us that empirical therapy without microbiologic studies is cost effective or rational in the light of this experience.
6 ReferencesJohn G. Bartlett, M.D.
Johns Hopkins University School of Medicine, Baltimore, MD 212051
Edelstein PH . Legionnaires' disease. Clin Infect Dis 1993;16:741-747
CrossRef | Web of Science | Medline2
Fine MJ ,Smith MA ,Carson CA , et al. Prognosis and outcomes of patients with community-acquired pneumonia: a meta-analysis. JAMA 1996;275:134-141
CrossRef | Web of Science | Medline3
Plouffe JF ,Breiman RF ,Facklam RR . Bacteremia with Streptococcus pneumoniae: implications for therapy and prevention. JAMA 1996;275:194-198
CrossRef | Web of Science | Medline4
Hofmann J ,Cetron MS ,Farley MM , et al. The prevalence of drug-resistant Streptococcus pneumoniae in Atlanta. N Engl J Med 1995;333:481-486
Full Text | Web of Science | Medline5
Bartlett JG . Diagnostic accuracy of transtracheal aspiration bacteriologic studies. Am Rev Respir Dis 1977;115:777-782
Web of Science | Medline6
Mundy LM ,Auwaerter PG ,Oldach D , et al. Community-acquired pneumonia: impact of immune status. Am J Respir Crit Care Med 1995;152:1309-1315
Web of Science | Medline
- Citing Articles (1)
Citing Articles
1
A. Endimiani, K. M. Hujer, A. M. Hujer, S. Kurz, M. R. Jacobs, D. S. Perlin, R. A. Bonomo. (2011) Are We Ready for Novel Detection Methods to Treat Respiratory Pathogens in Hospital-Acquired Pneumonia?. Clinical Infectious Diseases 52:Supplement 4, S373-S383
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