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The alveolar exudate of PCP is generally adherent to alveolar walls so that routine
sputum samples are insensitive for diagnosis. Use of induced sputum can increase sensitivity to
70% for PCP, but repeat testing does not increase this sensitivity.[658] Bronchoalveolar lavage
(BAL) is the most useful technique for diagnosis and can detect PCP in over 90% of cases,
compared with a tissue biopsy yield of 56%. The diagnostic yield can be increased to 95% with
multiple lung lobe sampling, particularly the upper lobes. BAL is the most useful technique for
diagnosis of opportunistic pulmonary infections in AIDS, particularly cytomegalovirus and
cryptococcosis.[409]
Fiberoptic bronchoscopy is an excellent method for diagnosis of pulmonary
complications and enables sampling by transbronchial biopsy (TBB), bronchial brushings (BB),
and bronchoalveolar lavage (BAL). With TBB, obtaining a larger number and/or size of
specimens provides a greater chance of making a specific diagnosis through reduction of
sampling error. The greatest diagnostic sensitivity (when the biopsy contains alveoli) is for
Pneumocystis jiroveci (carinii), between 60% to 100% for most reported series. Overall, the
diagnostic yield of TBB in AIDS is good. The complication rate for TBB is low.[659]
Fine needle aspiration (FNA) cytology can be useful for diagnosis. In cases of
Mycobacterium tuberculosis, FNA has a sensitivity of 46% with a specificity of 100%. Use of
PCR can increase the sensitivity to 84%.[409]
Bronchoscopy with BAL samples a large number of alveoli and the diagnostic sensitivity
exceeds that for induced sputum or TBB for diagnosis of PCP. Thus, BAL is the procedure of
choice for diagnosis of PCP.[660] Yield can be enhanced by sampling two areas of the lung
and/or by directing lavage to the area of lung with the most radiographic infiltrate, particularly
upper lobes. The overall diagnostic yield of BAL in patients with AIDS that present with
respiratory symptoms is greater than 50%. The most common agent found with BAL in this
setting is P jiroveci (carinii). Culture of BAL material for Mycobacterium tuberculosis (MTB)
can be useful, with a yield of 95%. Direct fluorescence antigen detection with culture for CMV
can be done, but a positive result does not always correlate with the presence of CMV
pneumonia, and CMV may be identified by BAL in half of HIV-infected persons. A BAL
procedure is useful when biopsy is contraindicated in patients with a coagulopathy or on
mechanical ventilators.[637,659]
By combining TBB and BAL, the diagnostic sensitivity for PCP and MTB approaches
100%, when adequate samples are collected. The high diagnostic sensitivity of TBB and/or BAL
for PCP has virtually eliminated the need for open lung biopsy. The sensitivity of BAL for PCP
in patients receiving aerosolized pentamidine is increased when BAL includes upper lobes.[609]
Unfortunately, TBB or BAL is less sensitive for diagnosing other pulmonary
complications of AIDS. Organisms such as Aspergillus, and Candida may be frequently
identified in BAL specimens, but may not necessarily be pathogens in some cases.[620,637,659]
The diagnostic yield of BAL is also reduced in HIV-infected patients who have received empiric
treatments for suspected infections prior to the performance of bronchoscopy with BAL, and the
results of BAL may lead to a change in treatment following definitive diagnosis.[661]
Kaposi's sarcoma (KS) may be difficult to identify on bronchoscopy because the bulk of
the tumor mass is below the mucosa. The low yield coupled with the risk for bleeding from
highly vascular KS lesions often precludes a biopsy diagnosis by bronchoscopy. A high-grade
lymphoma may involve the lungs in AIDS, but open lung biopsy is required for diagnosis.
Interstitial pneumonitis, either non-specific interstitial pneumonitis or lymphoid interstitial