Recent Advances in Pulmonary Medicine

N Engl J Med 1993; 329:1278-1279October 21, 1993

Article

To the Editor:

I congratulate Dr. Weinberger (May 13 and May 20 issues)1 for admirably performing a seemingly impossible task: summarizing recent advances in pulmonary medicine. I disagree, however, with his statement that in patients receiving aerosolized pentamidine the diagnostic yield of induced sputum for Pneumocystis carinii is diminished. Although Levine et al.2 reported a diminished yield with induced sputum in patients who had received prophylaxis with aerosolized pentamidine, when the data were analyzed on an intention-to-treat basis, there was no significant difference in yield. Three other studies address this question3-5. None reported a significant decrement in the diagnostic yield of induced sputum for P. carinii in patients who were receiving aerosolized pentamidine.

I know of several instances in which patients treated with prophylactic aerosolized pentamidine who had a suspected breakthrough of P. carinii pneumonia were referred for bronchoscopy without a prior examination of induced sputum. One cytology laboratory stopped analyzing sputum samples obtained from patients who had been receiving aerosolized pentamidine prophylaxis. If patients with suspected P. carinii pneumonia are denied induced-sputum analysis, they may be subjected to unnecessary bronchoscopy.

Mark L. Metersky, M.D.
Mount Sinai Hospital, Hartford, CT 06112

5 References

1
Weinberger SE. Recent advances in pulmonary medicine. N Engl J Med 1993;328:1389-97, 1462
Full Text | Web of Science | Medline

2
Levine SJ, Masur H, Gill VJ, et al. Effect of aerosolized pentamidine prophylaxis on the diagnosis of Pneumocystis carinii pneumonia by induced sputum examination in patients infected with the human immunodeficiency virus. Am Rev Respir Dis 1991;144:760-764
CrossRef | Web of Science | Medline

3
Kirsch CM, Jensen WA, Kagawa FT, Azzi RL. Analysis of induced sputum for the diagnosis of recurrent Pneumocystis carinii pneumonia. Chest 1992;102:1152-1154
CrossRef | Web of Science | Medline

4
Fahy JV, Chin DP, Schnapp LM, et al. Effect of aerosolized pentamidine prophylaxis on the clinical severity and diagnosis of Pneumocystis carinii pneumonia. Am Rev Respir Dis 1992;146:844-848
Web of Science | Medline

5
Metersky ML, Catanzaro A. Diagnostic approach to Pneumocystis carinii pneumonia in the setting of prophylactic aerosolized pentamidine. Chest 1991;100:1345-1349
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To the Editor:

Weinberger states that “pulse oximeters allow one to distinguish between oxygenated and reduced hemoglobin.” It is more accurate to state that pulse oximetry allows the differentiation of oxygenated and deoxygenated hemoglobin. Both these forms of hemoglobin are in the reduced state.1 Oxidized hemoglobin is methemoglobin; it is not the same as oxygenated hemoglobin.

David Wlody, M.D.
State University of New York, Brooklyn, NY 11203

1 References

1
The red blood cell. In: West JB, ed. Best and Taylor's physiological basis of medical practice. 11th ed. Baltimore: Williams & Wilkins, 1985:403.

To the Editor:

In discussing asthma, Weinberger stated that the most important factor in causation is that patients are allergic-atopic. Yet in the discussion of therapy, no mention is made of properly given desensitization injections as an important mode of immunotherapy.

Gerald N. Cohen, M.D.
St. Francis Hospital, Evanston, IL 60202

Author/Editor Response

Dr. Weinberger replies:

To the Editor: Dr. Metersky has appropriately pointed out that not all studies have shown a decreased diagnostic yield of induced sputum for P. carinii in patients receiving aerosolized pentamidine. A variety of confounding variables have been proposed to explain these differences in results1. Despite the unresolved issue and the variability of the numbers from study to study, I agree entirely that analysis of induced sputum remains useful in patients receiving aerosolized pentamidine and that it should not be bypassed in favor of bronchoscopy. Even in the study by Levine and colleagues,2 64 percent of the patients in whom P. carinii pneumonia developed while they were receiving aerosolized pentamidine had positive induced sputum (as compared with 92 percent of the patients who did not receive prophylaxis). Therefore, sputum induction can still eliminate the need for bronchoscopy in order to diagnose P. carinii in the majority of patients receiving aerosolized pentamidine.

I thank Dr. Wlody for pointing out that the correct term is “deoxygenated” rather than “reduced” hemoglobin. Somehow, “reduced hemoglobin” has slipped into common usage as well as into many articles and textbooks, and it unfortunately slipped into my article as well.

Dr. Cohen raises an important issue that remains quite controversial. Even though there is a strong association between allergy and asthma, it does not necessarily follow that desensitization is an effective and important form of therapy for asthma. As pointed out by Ohman3 in a review of allergen desensitization in the treatment of asthma, the benefit has been inconsistent. Some of the practical problems include the variability of antigen preparations, different regimens of administration, the need for prolonged therapy, and uncertainty about the need for desensitization against multiple antigens. Until there is better documentation of the clinical efficacy of allergen desensitization in adult asthma, this form of therapy is likely to remain an area of controversy.

Steven E. Weinberger, M.D.
Beth Israel Hospital, Boston, MA 02215

3 References

1
Fahy JV, Chin DP, Schnapp LM, et al. Effect of aerosolized pentamidine prophylaxis on the clinical severity and diagnosis of Pneumocystis carinii pneumonia. Am Rev Respir Dis 1992;146:844-848
Web of Science | Medline

2
Levine SJ, Masur H, Gill VJ, et al. Effect of aerosolized pentamidine prophylaxis on the diagnosis of Pneumocystis carinii pneumonia by induced sputum examination in patients infected with the human immunodeficiency virus. Am Rev Respir Dis 1991;144:760-764
CrossRef | Web of Science | Medline