Pneumonia due to Pneumocystis carinii is the most common life-threatening infection in patients with the acquired immunodeficiency syndrome (AIDS). It occurs at least once in some 60 percent of patients, and approximately one third of the pneumonic episodes are fetal. Despite an increasing awareness of other opportunistic infections in the syndrome, the proportion of patients who have had P carinii pneumonia by the time they are reported to the Centers for Disease Control has remained remarkably constant. As the incidence of AIDS is rising—notification rates are currently averaging 100 cases per week in the United States and ten per week in Europe—it is inevitable that an increasing number of chest physicians will be involved in the care of these patients.
Pneumocystis carinii has been recognized as a cause of pneumonia in immunosuppressed patients for approximately 40 years, and important advances have been made in the treatment and prophylaxis of the pneumonia, especially in patients receiving immunosuppressive therapy for malignant disease or organ transplantation. Patients with AIDS, however, present a special problem: diagnosis of Pneumocystis pneumonia in these patients is frequently delayed because the symptoms tend to develop gradually, often in previously healthy subjects, and treatment is complicated by an unusually high incidence of adverse reactions to specific therapeutic agents. Furthermore, these individuals have a very poor prognosis, irrespective of the treatment they receive: the median survival time of AIDS patients with P carinii pneumonia ranges from 35 weeks in patients with Pneumocystis pneumonia alone, to 44 weeks when there is coexistent Kaposi’s sarcoma. The overriding priorities of management, therefore, are comfort and quality of life. It is espe-dally important that all diagnostic and therapeutic decisions be tempered by compassion and attention to the individual patients needs.
Clinical and Roentgenographic Features
The clinical and roentgenographic features of Pneumocystis pneumonia are nonspecific, and diagnosis may require a high degree of suspicion. It is important to enquire about sexual preference, especially in men, and intravenous drug abuse, in any patient with unexpected respiratory symptoms or an unexplained abnormality on chest x-ray film. Symptoms often develop more gradually than in other immunosup-pressed individuals with P carinii pneumonia, but it is worth remembering that the infection can present abruptly in these patients. Malaise, fever, nonproductive cough, and dyspnea are the usual symptoms, but chills and chest pain may also occur, and some patients do produce sputum. Oral candidiasis or generalized lymphadenopathy, though not always present, are useful clues to the diagnosis of AIDS, but physical signs in the chest are often unimpressive or absent The chest roentgenogram typically shows difluse bilateral pulmonary infiltrates, although the infiltrates may be confined to the upper or lower zones, and they are occasionally unilateral at the time of presentation. In up to 5 percent of cases, however, the lungs are roent-genographically clear, and this figure may well increase as patients are seen earlier in the disease. Enlarged hilar or mediastinal lymph nodes have been described in as many as one third of patients, but pleural effusions are uncommon and more suggestive of Kaposis sarcoma. Latest news about medicine is published on canadian Neighbor Pharmacy.
Choice of Procedure
Diagnosis of P carinii pneumonia rests on identification of the organism in lung tissue or respiratory secretions. There are no serologic tests for identifying patients with active disease. A number of studies have demonstrated the value of fiberoptic bronchoscopy as a method of obtaining suitable specimens. In the series from a recent workshop of the National Heart,
Lung and Blood Institute (NHLBI), a retrospective study of the pulmonary complications of AIDS in six centers over a three-year period, bronchoscopy was performed in 368 episodes of Pneumocystis pneumonia and the diagnosis was established in 348 (95 percent) of them. Fixed tissue specimens and touch imprints of tissue, both obtained by transbronchial biopsy, had diagnostic yields of more than 93 percent; bronchoalveolar lavage fluid alone had a yield of 79 percent; and although the yield with brush biopsies was only 37 percent, there were four instances in which these provided the only positive specimen. In a number of smaller published studies, the results with bronchoalveolar lavage have been even more impressive, with yields comparable to those of transbronchial biopsy, possibly because the NHLBI analysis did not distinguish true bronchoalveolar lavage, in which the bronchoscope is wedged into a subsegmen-tal bronchus before instilling and withdrawing fluid, from bronchial washings, in which only the proximal large airways are irrigated. The relatively low diagnostic yield from bronchial brushing, a feature of most though not all studies, probably reflects the mainly intraalveolar localization of P carinii. Bron-choscopic procedures are effective for diagnosing the other pulmonary complications of AIDS, with the exception of Kaposis sarcoma, and they are also relatively safe in these patients: transbronchial biopsy carries the usual 5 to 8 percent risk of pneumothorax, but significant hemoptysis is rare, and there have been no deaths. Fiberoptic bronchoscopy is therefore the diagnostic procedure of choice in all patients with AIDS or suspected AIDS who are thought to have P carinii pneumonia. In patients with bleeding disorders and patients undergoing mechanical ventilation, the procedure should be restricted to bronchoalveolar lavage, but in all other subjects, the bronchoscopy should probably include transbronchial biopsy as well, with touch imprints of tissue in addition to fixed tissue specimens. Ideally, bronchial brush biopsies should be obtained at the same time, but brushing ought not to be performed alone. Open lung biopsy should be considered only in patients who have had a nondiagnostic bronchoscopy, and even then it is often preferable to repeat the bronchoscopy first.
Indications for Bronchoscopy
Although fiberoptic bronchoscopy provides a safe and highly effective means of obtaining pulmonary specimens in patients with AIDS and Pneumocystis pneumonia, there are a number of issues regarding its use which need to be clarified by further study.
The first issue concerns previously healthy subjects from high risk groups for AIDS who present with pulmonary symptoms but have a normal chest roentgenogram. Which of these patients should undergo bronchoscopy? A variety of noninvasive studies have been performed in an attempt to select the patients most likely to have Pneumocystis pneumonia. The arterial oxygen tension is a relatively insensitive screening test, as it is normal (>80 mm Hg) in approximately 20 percent of patients with Pneumocystis pneumonia and AIDS. The alveolar minus arterial partial pressure of oxygen may be more sensitive, but it is still unclear whether the measurement must be made on exercise in order to be useful. The diffusing capacity for carbon monoxide (Deo) is less than 70 percent of the predicted value in almost all patients with AIDS and P carinii pneumonia, but low values are also seen in high risk patients without AIDS. The gallium scan is another highly sensitive method for detecting Pneumocystis pneumonia: when read in the conventional way, it also has a low specificity, but in a recent study of 22 AIDS patients, the specificity was increased to 90 percent, while retaining 100 percent sensitivity, by using a graded scoring system for pulmonary uptake of the nuclide. Gallium scanning is expensive, and takes one to three days to complete, but these findings are encouraging and justify further assessment of the technique.
The second issue concerns patients who have had a previous episode of Pneumocystis pneumonia. Patients with AIDS who have clinically recovered from P carinii pneumonia sometimes fail to eliminate the organisms from their lungs. Three to six weeks after starting specific therapy, 25 to 67 percent of AIDS patients still have P carinii detectable in pulmonary tissue or lavage specimens. There are insufficient data to know how much longer the organisms persist, and it is unclear whether the persistent forms observed are all viable and pathogenic. However, they may complicate the interpretation of subsequent diagnostic procedures. The identification of P carinii during a second pneumonic episode, therefore, is of unknown significance, and it is particularly important to attempt to exclude other causes of pulmonary infiltrate before concluding that there is a recurrence of Pneumocystis pneumonia.
A third issue is whether bronchoscopy could be replaced by an even simpler procedure in some patients. One technique under investigation is the collection of pulmonary lavage fluid with a disposable catheter introduced through the mouth, while the preliminary findings of another study indicate that most cases of Pcarinii pneumonia in AIDS can even be diagnosed from induced sputum. The effectiveness of these techniques for diagnosing other infections, and their value in patients with normal chest roentgenograms, have not been determined, but the procedures are safe and inexpensive, and they promise to be useful as screening tests, especially in centers with larger numbers of AIDS patients.