Approach

Most cases of invasive aspergillosis (IA) occur in patients with underlying immune deficiency. Close attention should be paid to the immune status of the patient. Patients at high risk of IA are those with severe, prolonged (>10 days) neutropenia, and allogeneic stem cell recipients with acute or chronic graft-versus-host disease (GVHD).

IA should also be considered in:

  • Solid organ transplant recipients (particularly in lung and/or heart recipients)

  • Patients with chronic granulomatous disease (CGD)

  • Patients receiving high-dose corticosteroids or other immunosuppressive drugs

  • Patients with poorly controlled diabetes mellitus

  • Patients with primary immunodeficiency disorders.

The lack of specific clinical features impedes diagnosis. Early diagnosis is paramount to reduce mortality and morbidity. In the high-risk patient with clinical signs and symptoms suspicious of IA, a high resolution computed tomography (CT)/magnetic resonance imaging (MRI) scan, biomarkers (e.g., Aspergillus galactomannan, serum beta-D-glucan), sputum examination, bronchoalveolar lavage (BAL) fluid examination, and tissue biopsy for histopathology and culture of microorganism are helpful in the diagnosis.

Molecular tests such as polymerase chain reaction (PCR) testing of BAL fluid and/or tissue specimen are useful in the early diagnosis of IA.[66] [ Cochrane Clinical Answers logo ]

Chronic pulmonary aspergillosis (CPA) should be considered in patients with chronic lung disease and radiographs showing intracavitary mass lesions. These are usually incidental findings on a routine chest x-ray (CXR) or during evaluation of hemoptysis. Guidelines suggest that diagnosis of CPA requires imaging, direct evidence of Aspergillus infection or an immunologic response to Aspergillus and exclusion of other diagnoses, with disease present for at least 3 months.[2][3] See Diagnostic criteria.

Clinical manifestations

Invasive pulmonary aspergillosis presents with fever, mild to moderate nonproductive cough, and pleuritic chest pain. Pleuritic chest pain in a neutropenic patient or in a stem cell recipient with GVHD should raise strong suspicion of IA. Hemoptysis may be present and may suggest the presence of a lung lesion eroding into a neighboring blood vessel. Catastrophic hemoptysis may occur, particularly with recovery of neutrophils after chemotherapy. Dyspnea may be present, suggesting extensive lung involvement, and may be seen with rejection of a transplanted lung.

Invasive sinus disease may present with headache, congestion, facial pain with or without sinus drainage, or sinus tenderness. Concomitant involvement of sinus and lungs may occur.

Extension of sinus disease into the eye/brain may lead to proptosis, cranial nerve palsies, altered mental status, and seizures.

Skin involvement is not uncommon in IA. Single or multiple discrete, erythematous, mildly tender nodules of varying sizes with a necrotic and often ulcerated center (ecthyma gangrenosum) are mostly seen in immunocompromised patients. They may occur in disseminated disease or local invasion after trauma. Occasionally, burns or surgical wounds may be infected with Aspergillus.

Symptoms of CPA include a chronic cough, breathlessness, chest discomfort, weight loss, and malaise.[4] Simple aspergilloma is mostly asymptomatic. It can present as a self-limiting mild hemoptysis; however, severe hemoptysis may occur in a minority of cases.

Imaging

Pulmonary invasive aspergillosis (IA)

  • CXR may reveal nodules, consolidation, or frequently nonspecific infiltrates. Often CXR shows no abnormalities. If index of suspicion is high, chest CT scan should be obtained.

  • High-resolution CT scan of chest is the preferred radiologic method as it is useful in detecting early lesions suggestive of pulmonary aspergillosis. The scan may show single or multiple nodules scattered over 1 or both lungs, generally in the periphery of the lung fields. Smaller nodules (<1 cm), ground-glass opacities, and consolidation are nonspecific features and do not necessarily suggest pulmonary IA.[67] The presence of macronodules (1 cm or larger) in a high-risk patient is highly suggestive of IA, and may be seen in other conditions including other invasive fungal infections, tuberculosis, nocardiosis, and bacterial infections.[67] In the leukemic patient with neutropenia, early disease is characterized by a haziness representing hemorrhage/edema surrounding the nodules ("halo sign").[68] With clinical improvement (e.g., reversal of underlying immune deficiency), the halo sign may disappear. The "air-crescent sign" can be observed instead. It is indicative of a necrotic lesion contracting from viable lung tissue, creating a cavity within where the air is trapped. The halo sign is indicative of early disease and thus is useful in early diagnosis, while the air-crescent sign indicates that the disease has been present for >6 to 7 days. Therapy initiated in patients with halo sign is associated with improved outcome.[69] During therapy, the nodular lesions initially enlarge, suggesting that the process may be worsening. After about 7 days of therapy, however, CT scans show improvement. Pulmonary macronodules, the halo sign, and the air-crescent sign have been best studied in patients with IA and hematologic malignancy or stem cell transplantation. Radiologic features are not as well characterized in other settings with IA.

Invasive aspergillosis at other sites (e.g., skin, brain, sinuses)

  • IA suspected at other sites such as sinuses and brain may also be evaluated with CT scan or MRI. X-rays of the sinuses are not helpful. CT is the preferred imaging modality.[68][67] With sinus disease, in addition to the opacity/mass within the sinus cavity, bone erosion of the surrounding sinus walls is highly suggestive of an aggressive infection. In brain disease, space-occupying lesions with surrounding edema, abscesses, and hemorrhage can be seen.

CPA

  • CXR may reveal one or more lung cavities with or without aspergilloma, infiltrates, nodules, pleural thickening, parenchymal damage, and fibrosis.[3][4][70] X-ray is the initial imaging method, but CT scan can provide better definition and location of findings.[3]

Aspergilloma

  • Single upper lobe lesions are the most common finding on CXR. Multiple lesions are rarely seen. An upper lobe, mobile, intracavitary mass with an air-crescent in the periphery (Monod's sign) is strongly suggestive of aspergilloma. Plain x-rays are usually adequate. Occasionally chest CT is required. In radiographs a change in the position of the fungal ball may be seen with a change in the position of the patient.[71] Periodic CXRs are adequate for the follow-up of asymptomatic aspergilloma.

    [Figure caption and citation for the preceding image starts]: "Halo" sign in early pulmonary aspergillosisFrom the collection of Dr P. Chandrasekar; used with permission [Citation ends].com.bmj.content.model.Caption@775411da[Figure caption and citation for the preceding image starts]: "Air-crescent" sign in late pulmonary aspergillosisFrom the collection of Dr P. Chandrasekar; used with permission [Citation ends].com.bmj.content.model.Caption@58db66fd

Serology/bronchoalveolar lavage (BAL)

Invasive aspergillosis

  • The diagnosis of IA has remained a challenge due to the nonspecific clinical presentation of IA, the low sensitivity of microscopy and culture of lower respiratory specimens, and the difficulty of obtaining tissue for histopathology in critically ill patients. As a result, biomarkers such as Aspergillus galactomannan (GM) antigen and serum beta-D-glucan have been evaluated, mostly in stem cell recipients and leukemic patients with neutropenia.[72][73][74]

  • Galactomannan (GM) antigen

    • GM antigen is a polysaccharide cell wall component of Aspergillus species that is released into the systemic circulation during fungal growth in tissue.

    • A double-sandwich enzyme-linked immunosorbent assay (ELISA) method exists for detection of GM (optical density index 0.5 or greater on 2 occasions is positive).[75][76]

    • The combination of a high-risk patient with suggestive clinical and radiologic (CT scan) findings and a positive serum GM may be considered adequate for a diagnosis of "probable" IA, thus avoiding invasive procedures such as tissue (lung) biopsy.[77][78]

    • The sensitivity and specificity of serial serum GM is 67% to 100% in acute leukemia patients and 86% to 98% in stem cell recipients, respectively.[76][77]

    • Serial monitoring of GM has detected IA between 6 and 14 days earlier than radiographic findings.[79]

    • False-positive results are seen with other fungi such as Histoplasma, Blastomyces, Geotrichum, and Penicillium species, and bacteria (e.g., Bifidobacterium).[72][80] The use of beta-lactam antibiotics such as piperacillin-tazobactam and amoxicillin-clavulanic acid may show false-positive results.[81] In the presence of mold-active drugs used as prophylaxis or therapy, the sensitivity of GM assay is reduced. The sensitivity may be lower in non-neutropenic patients, possibly due to a lower fungal burden.

    • The combined use of serum GM antigen assay and chest CT improves the detection of pulmonary IA, permitting earlier initiation of therapy.[78] Data suggest that GM antigen measurements in BAL fluid are more sensitive than serum GM and have a better predictive value, and BAL GM antigen test has now become an accepted method for diagnosis.[82][83] BAL fluid GM antigen measurement of 1.5 optical density index or higher appears to be a strong predictor of IA in immunocompromised patients (specificity >90%).[84]

  • Serum (1-3)-beta-D-glucan

    • (1-3)-beta-D-glucan is a component in the cell wall of many fungi (with the exception of Zygomycetes and Cryptococcus), and a serologic diagnostic method for invasive fungi.[73][74]

    • This test is a variation of the limulus assay used to detect endotoxin. The presence of serum glucan is not specific for Aspergillus and false-positive results can occur due to blood collection tubes, gauze, and contaminated membrane filters.

    • One Cochrane review found wide variation in sensitivity and specificity of commercially available tests for serum (1-3)-beta-D-glucan in detecting selected invasive fungal infections, including aspergillosis. Sensitivity ranged from 27% to 100%, and specificity ranged from 0% to 100%; therefore, accuracy of diagnosis could not be determined.[85] [ Cochrane Clinical Answers logo ] ​

  • Polymerase chain reaction (PCR)

    • Polymerase chain reaction diagnosis, based on amplification of Aspergillus-specific fungal genes (usually ribosomal DNA) in blood and BAL fluid, has shown considerable promise for early diagnosis. In BAL fluid, two positive PCR test results have a higher positive predictive value to rule in IA.[66] [ Cochrane Clinical Answers logo ] ​ PCR testing in histopathology specimens also increases the diagnostic yield.[66] PCR-based test results may be falsely positive because of ubiquitous presence of Aspergillusconidia. Combining the PCR-based test with other noninvasive nonculture-based diagnostic methods (i.e., serum GM test and serum beta-D-glucan assay) is an important area for early diagnosis of invasive aspergillosis.

CPA

In patients with imaging and history suggestive of CPA, diagnosis can be confirmed with serum Aspergillus immunoglobulin G (IgG) or precipitins, or Aspergillus antigen or DNA in respiratory fluids.[3]

  • Aspergillus antibodies

    • Aspergillus IgG antibody test is the most sensitive test for chronic cavitary pulmonary aspergillosis (CCPA).[2] Serum IgG antibodies to Aspergillus or precipitins are positive in most patients with CPA.

    • False-negative cases may be seen in patients receiving corticosteroid therapy or in those with aspergilloma due to species other than A fumigatus.[86]

  • GM antigen

    • When used in the diagnosis of CPA, BAL fluid should be used (not serum). Specificity and sensitivity is lower than Aspergillus antibody tests.[3]

  • PCR

    • Sensitivity of PCR testing of respiratory secretions is lower than antibody testing, but higher than culture.[2][87]

Microbiology

Pulmonary invasive aspergillosis (IA)

  • Cough is generally nonproductive in these patients. Sputum, when available, is usually negative by fungal stain and culture. A positive finding is highly significant in a high-risk patient (immunocompromised).[11] However, in a low-risk patient (immunocompetent), Aspergillus in sputum may simply represent colonization needing no further intervention.[11][88]

  • Aspergillus species grow well on standard media and can be identified to a species level in most laboratories. Culture from a sterile site is diagnostic of IA. Blood cultures are usually negative even in disseminated cases.

  • Commonly used invasive diagnostic procedures are:

    • Bronchoscopy with BAL and/or biopsy

    • Percutaneous transthoracic CT-guided needle aspiration

    • Video-assisted thoracoscopic biopsy.

  • Specimens obtained may show characteristic angular, dichotomously branching, septate hyphae, and Aspergillus species in culture. Culture confirmation is critical to distinguish Aspergillus from other fungi with similar morphologic features, such as Fusarium and Scedosporium.[17] False-negative results occur with specimens obtained from unaffected areas, with inadequate specimens, and in patients already receiving antifungal therapy. Thus, lack of positive fungal smear or culture does not rule out the diagnosis of IA. Also, invasive procedures may not be possible in critically ill patients or those with thrombocytopenia.

Invasive aspergillosis at other sites (e.g., skin, brain, sinuses)

  • Appropriate tissue specimens obtained by biopsy must be submitted for fungal stain (Gomori methenamine silver) and culture. Gram stain to detect bacteria is inappropriate for fungal detection. Optical brighteners using white stain are helpful in enhancing fungal elements.

[Figure caption and citation for the preceding image starts]: Gomori methenamine silver (GMS) of lung tissue showing dichotomously branching, septate hyphae of AspergillusFrom the collection of Dr P. Chandrasekar; used with permission [Citation ends].com.bmj.content.model.Caption@3397f887

CPA

  • Direct microscopy or fungal culture of respiratory specimens may identify the presence of Aspergillus. However, culture positivity rates vary widely and results should be interpreted with caution.[3][89] Testing multiple samples increases the probability of a positive culture or microscopy test, but the majority of patients have negative sputum cultures.[2] Additionally, as Aspergillus are ubiquitous in the environment, their presence in sputum is not necessarily diagnostic.[89]

Histopathology

Invasive aspergillosis (IA)

Tissue biopsy is the most definitive method of diagnosis. Biopsy may be obtained by:

  • Transbronchial CT-guided needle aspiration (for peripheral lesions)

  • Video-assisted thoracoscopic surgery (VATS) biopsy

  • Open lung biopsy.

VATS is the preferred method, as biopsy is obtained under direct vision and is less invasive compared with open lung biopsy. Specimen obtained by a transbronchial or CT-guided approach is generally suboptimal and may be associated with complications such as uncontrolled bleeding or pneumothorax. Thrombocytopenia is common in leukemia and stem cell recipients, making invasive procedures hazardous. Often a biopsy procedure cannot be performed in view of platelet transfusion-refractory thrombocytopenia or severe illness, thus leading clinicians to make empiric treatment choices.

Other biopsy sites may include skin, sinus tissue, brain or, uncommonly, bone, heart, pericardium, or abdominal organs.

Specimens obtained by biopsy must be sent in saline for microbiologic culture and in formalin for pathology. Acute-angle branching, septate, narrow hyphae, with tissue invasion and surrounding inflammatory infiltrates along with necrosis, are findings highly suggestive of IA.[17] As Aspergillus is angioinvasive, the organism is frequently found within the vasculature, causing thrombosis, tissue infarction, and coagulative necrosis. Other fungi such as Fusarium and Scedosporium ( Pseudoallescheria) may have similar features requiring culture confirmation of the organism.

CPA

  • In certain cases, microscopic examination of tissue obtained by biopsy is necessary for diagnosis.

  • In CCPA, biopsy may show inflammatory cells, fibrosis, granulomata, and hyphae.[2] If hyphae are invading the lung parenchyma, then acute or subacute IA is diagnosed.[3]

  • Examination of aspergilloma shows fungal mycelia, inflammatory cells, tissue debris, fibrin, and mucus.[4]

  • Aspergillus nodules are diagnosed after excision biopsy, usually following suspicion for malignancy. Single nodules that are completely excised may not need any further treatment.[3][4][Figure caption and citation for the preceding image starts]: Diagnostic algorithm for suspected invasive aspergillosisCreated by authors [Citation ends].com.bmj.content.model.Caption@3cdc4489

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