ACR Appropriateness Criteria®
Clinical Condition: Acute Respiratory Illness in HIV + Patient
Variant 1: Asymptomatic.
| Radiologic Exam Procedure |
Appropriateness Rating |
Comments |
| X-ray, chest |
2 |
|
| CT, chest |
2 |
|
| NUC, lung, gallium 67 scan |
2 |
|
| NUC, lung, DTPA-Tc scan |
2 |
|
Appropriateness Criteria Scale
1 2 3 4 5 6 7 8 9
1 = Least appropriate 9 = Most appropriate
|
Note: Abbreviations used in the tables are listed at the end of the "Major Recommendations" field.
Variant 2: Cough, dyspnea, chest pain, fever.
| Radiologic Exam Procedure |
Appropriateness Rating |
Comments |
| X-ray, chest |
9 |
|
Appropriateness Criteria Scale
1 2 3 4 5 6 7 8 9
1 = Least appropriate 9 = Most appropriate
|
Variant 3: Negative, equivocal, or nonspecific chest radiograph.
| Radiologic Exam Procedure |
Appropriateness Rating |
Comments |
| CT, chest |
8 |
|
| NUC, lung, gallium 67 scan |
2 |
|
| NUC, lung, DTPA-Tc scan |
2 |
|
Appropriateness Criteria Scale
1 2 3 4 5 6 7 8 9
1 = Least appropriate 9 = Most appropriate
|
Note: Abbreviations used in the tables are listed at the end of the "Major Recommendations" field.
Variant 4: Positive chest radiograph, diffuse infiltrates.
| Radiologic Exam Procedure |
Appropriateness Rating |
Comments |
| CT, chest |
4 |
|
| NUC, lung, gallium 67 scan |
2 |
|
| NUC, lung, DTPA-Tc scan |
2 |
|
Appropriateness Criteria Scale
1 2 3 4 5 6 7 8 9
1 = Least appropriate 9 = Most appropriate
|
Note: Abbreviations used in the tables are listed at the end of the "Major Recommendations" field.
Variant 5: Positive chest radiograph, infection other than PCP suspected.
| Radiologic Exam Procedure |
Appropriateness Rating |
Comments |
| CT, chest |
4 |
|
| NUC, lung, gallium 67 scan |
2 |
|
| NUC, lung, DTPA-Tc scan |
2 |
|
Appropriateness Criteria Scale
1 2 3 4 5 6 7 8 9
1 = Least appropriate 9 = Most appropriate
|
Note: Abbreviations used in the tables are listed at the end of the "Major Recommendations" field.
Variant 6: Positive chest radiograph, noninfectious disease suspected.
| Radiologic Exam Procedure |
Appropriateness Rating |
Comments |
| CT, chest |
8 |
|
| NUC, lung, thallium scan |
2 |
|
| NUC, lung, gallium 67 scan |
2 |
|
Appropriateness Criteria Scale
1 2 3 4 5 6 7 8 9
1 = Least appropriate 9 = Most appropriate
|
Note: Abbreviations used in the tables are listed at the end of the "Major Recommendations" field.
Acute respiratory illness (ARI) constitutes a group of signs and symptoms that develop over a brief interval (hours to weeks), some of which are constitutional such as fever, chills, and weight loss, and some of which are organ specific such as cough, shortness of breath, and chest pain. In human immunodeficiency virus (HIV)-infected individuals with ARI, a wide variety of diseases can have similar presentation. Clinical and demographic factors that help to rank the differential diagnosis include the degree of immunosuppression as reflected by the patients' CD4 cell count, whether or not they are being treated with highly active antiretroviral therapy (HAART), their country or region of origin and travel history, and their HIV risk factor. Radiographic findings play a role in narrowing the differential diagnosis and in guiding further diagnostic testing or procedures.
The chest radiograph is a basic and widely accepted diagnostic imaging tool in HIV-infected patients. When an HIV-infected patient presents with ARI, after obtaining the history and performing a physical examination, obtaining a chest radiograph is usually the next step. The vast majority of processes that cause ARI in HIV-infected individuals are associated with chest radiographic abnormalities, and several studies support obtaining an initial chest radiograph in HIV-infected patients with an ARI.
The nature and distribution of pulmonary findings on the chest radiograph will often suffice in suggesting a diagnosis or differential diagnosis. Bacterial pneumonia caused by infection with the usual organisms is the most common cause of ARI in acquired immune deficiency syndrome (AIDS) patients. The chest radiographic finding of focal or multifocal consolidation associated with fever, sputum production, and leukocytosis is usually diagnostic. Viral pneumonia can also present with bilateral reticular opacities on chest radiographs. If the viral infection is cytomegalovirus, there will often be cytomegalovirus infection in other organs (e.g., retinitis, esophagitis), and the patients will have very low CD4 counts (less than 50/mm3). On CT, cytomegalovirus will often demonstrate small, ill-defined nodules, peribronchial thickening, and foci of bronchiectasis. Congestive heart failure due to AIDS cardiomyopathy can also show reticular interstitial opacities. If bilateral nodular or reticular opacities are present without lymphadenopathy or pleural effusion and the CD4 count is less than 200/mm3, a diagnosis of Pneumocystis jiroveci pneumonia (PCP) can be suggested. Several studies found that the severity of the radiographic abnormality correlated with both severity of illness and mortality in patients with PCP.
It is now accepted that a normal or only subtly abnormal chest radiograph can occasionally occur in patients with tuberculosis, cytomegalovirus pneumonia, and PCP among other processes. If there is a high clinical suspicion of a pulmonary infection in the setting of a normal chest radiograph, a CT may be warranted to assess for subtle abnormalities. Miliary or disseminated tuberculosis or nodal disease can be readily evident on CT in the face of a normal or near-normal chest radiograph. Small airways disease with mild bronchiectasis, peribronchial thickening, foci of mucoid impaction, and air trapping may be evident only on CT. Patients who have a normal chest radiograph and PCP will usually have focal areas of ground glass opacity evident on CT.
Exercise desaturation, an elevated lactate dehydrogenase (LDH), and a low diffusion capacity are all associated with PCP and add supportive evidence to a typical chest radiographic appearance. Sputum induction will often confirm the diagnosis. In the setting of a negative sputum induction, some practices treat empirically for PCP if the chest radiographic and clinical findings are typical. Otherwise, fiberoptic bronchoscopy (FOB) with bronchoalveolar lavage and/or biopsy is the usual practice. One group of researchers proposed some compelling arguments for using CT early in the diagnostic evaluation of PCP. When the presence or absence of ground glass opacity on CT was used as the diagnostic criterion, patients were classified as "possible PCP" or "not PCP." CT had a high sensitivity and specificity. This is supported by the findings of one study that found ground glass, reticular, and cystic changes in the lung on high resolution CT (HRCT) in patients with PCP. In contrast, those with tree-in-bud nodules had other diagnoses. The authors concluded that patients with "possible PCP" should go on to direct testing, (induced sputum, bronchoalveolar lavage) whereas a diagnosis of "not PCP" can be used to avoid empiric treatment and direct testing. They also point out that CT has higher sensitivity and specificity and is cheaper than gallium scanning and provides an immediate result, in contrast to the 48 to 72-hour delay for gallium. There is, however, literature supporting the utility of performing DTPA-Tc and gallium 67 lung scans in patients with suspected PCP and negative or atypical chest radiographs. In two different studies, gallium lung scans were positive (94% and 100%, respectively) in patients with PCP. In another study, the researchers noninvasively detected 34 of 36 patients with PCP using a combination of DTPA lung scanning while inducing sputum and were thus able to reduce the need for bronchoscopy.
CT is widely accepted when noninfectious AIDS-related intrathoracic diseases are suspected, when the chest radiograph shows findings atypical for PCP, or when FOB is not diagnostic. The CT findings can frequently suggest the diagnosis or at least limit the diagnostic possibilities, and may identify optimal sites for obtaining a biopsy. According to another group of researchers, in a series of 128 AIDS patients, they found that CT was 93% accurate in excluding disease and 94% and 93% accurate in rendering confident diagnoses of PCP and Kaposi sarcoma, respectively. Another study demonstrated the utility of thallium and gallium scanning for diagnosing Kaposi sarcoma. In this series, a thallium-positive, gallium-negative pattern had a high specificity of 95% for the diagnosis of Kaposi sarcoma. However, the sensitivity decreased from 89% to 37% in patients who had opportunistic infections.
If lung nodules or masses with or without cavitation are present on the chest radiograph and the sputum is unrevealing, a chest CT should be performed. CT better delineates the distribution and morphology of the parenchymal disease. CT also has an advantage in demonstrating associated hilar and mediastinal lymphadenopathy, which may alter the differential diagnosis. The differential diagnosis for lung nodules and masses depends in part on the patient's immune status and HIV risk factors. Bacterial infection can occur at any level of immunity, although its frequency increases as CD4 declines, and it occurs more often in HIV-infected patients whose risk factor was intravenous drug use. In one series of studies, bacterial infection was the most common etiology of lung nodules seen on CT. Tuberculosis was second. In areas where fungal infections are endemic, that diagnosis rises in the differential diagnosis. The authors noted that nodule size less than 1cm, fever, and cough favored an infectious etiology for the nodules. Neoplasms also can cause nodules and masses. Kaposi sarcoma has its highest prevalence in HIV-infected gay men. In that population, especially if the patient has a low CD4 count and cutaneous or oropharyngeal Kaposi sarcoma, lung nodules and masses will often be due to Kaposi sarcoma. The radiographic findings can mimic infection. Acutely, patients with Kaposi sarcoma can present with hemoptysis. FOB with bronchial inspection will reveal the typical violaceous endobronchial Kaposi sarcoma lesions in most cases. AIDS-related lymphoma is predominantly an extranodal disease. Lung nodules and masses are often present if there is thoracic involvement. These patients are often acutely ill with "B" symptoms. CT will often show lymphadenopathy or abdominal visceral involvement that is not evident on the chest radiograph.
Lymphadenopathy may be evident on chest radiographs, although CT is much more sensitive in its detection. When an HIV-infected patient is acutely ill and has lymphadenopathy, the differential diagnosis includes tuberculosis, other mycobacterial infections, fungal infection, and lymphoma among more common etiologies. In patients with tuberculosis who are evaluated with contrast-enhanced CT, central low attenuation lymphadenopathy is highly suggestive of the correct diagnosis. The pattern of associated parenchymal and pleural disease, described above, will also help prioritize the differential diagnosis.
Pleural effusions are rarely present in patients with PCP. Bacterial pneumonia, tuberculosis, and fungal infections all can be associated with pleural effusions. Kaposi sarcoma may have effusions in the later stages. Kaposi sarcoma effusions are often hemorrhagic. Pleural involvement with AIDS-related lymphoma is not rare. Patients may have effusions or masses. While the chest radiograph is usually adequate to demonstrate the presence of a pleural effusion, if the patient does not respond to antibiotic therapy or develops a complicated effusion, CT may be helpful in guiding the choice of a site for biopsy or drainage.
Recommendation
Chest radiography is indicated early in the evaluation of AIDS patients with ARI. Most respiratory diseases will be associated with abnormal chest radiographic findings. If the radiograph is normal or equivocal and clinical suspicion for disease is high, CT can be performed to evaluate for subtle pulmonary abnormalities and lymphadenopathy. CT also plays a role in weighting a differential diagnosis and guiding diagnostic and therapeutic procedures in those with abnormal chest radiographs. Nuclear scintigraphy, including gallium 67 and DTPA-Tc, can be helpful in diagnosing PCP, and the combination of thallium and gallium scanning has shown utility in the diagnosis of Kaposi sarcoma.
Abbreviations
- CT, computed tomography
- NUC, nuclear medicine
- DTPA-Tc, Diethylenetriamine pentaacetic acid-Technetium
- PCP, Pneumocystis jiroveci pneumonia
