Data from a German study shows, during the period from 1979 to 1992, the incidence of invasive mycosis increased by about 8 times, and IPA, as the most harmful type and the most fatal type of pulmonary aspergillosis infection, has gradually been paid attention by clinical researchers14. Clinically, IPA is generally divided into neutropenia and non-neutropenia. This study mainly discusses the diagnostic methods of IPA patients with non-neutropenia. We found that IPA in nonneutropenic patients showed a specific progressive deterioration in the CT scan in a short interval, which promoted early diagnosis and timely antifungal therapy. The diagnosis of IPA was validated finally by therapeutic response and/or biopsy. Therefore, our findings provide a noninvasive, feasible and effective strategy for early diagnosis of IPA with URD. To the best of our knowledge, the current report is the first to emphasize the diagnostic value of dynamic monitor of CT scans in IPA with URD.
Research data shows that IPA is commonly diagnosed in neutropenic patients, but also could be diagnosed in nonneutropenic patients with URD5, 15. In our data, all patients had no neutropenia but less severe forms of immunocompromise in lungs. Most of the reasons for their admission are COPD, asthma and pneumonia, complicated with prostate cancer, hospital acquired pneumonia (HAP), and most of them have underlying diseases such as coronary heart disease, hypertension, and diabetes. Some patients have a history of malignant tumors. So we suggest to keep IPA in mind when managing the patients in Department of Respiratory Medicine. URD of those patients could further increase the complexity of Aspergillus diagnosis. First, pulmonary diseases commonly share same symptoms and signs with IPA, such as fever, dyspnea, chest tightness, wheezing and sputum production. And those non-specific symptoms and signs could mask Aspergillus infections. Second, corticosteroids and broad-spectrum antibiotics are used commonly even overused in these population, which could increase risk for IPA4, 5. Third, biomarkers and specific CT signs of IPA are not sensitive in nonneutropenic patients. The specific CT signs like cavity or air crescent are less common in nonneutropenic patients than in neutropenic patients8. In agreement with another report16, the most common CT finding was consolidation. Such CT signs are non-specific and might correspond to a wide range of morbidities such as bacterial pulmonary infection, cardiac failure, aspiration pneumonia and so on. At last patients’ poor clinical conditions like weakness, dyspnea, hypoxic respiratory failure and cardiac failure made invasive procedures such as lung tissue biopsy and bronchoscopy risky. As in our report, only one patient received biopsy. Yet tissue biopsy and lower respiratory tract samples for culture or GM tests in BALF are very specific for IPA 10, 17.
GM is a universal polysaccharide component in the cell wall of Aspergillus, which is a polyantigen. GM appears in circulation about 1 week earlier than clinical symptoms and imaging abnormalities. Continuous monitoring of patients' serum GM levels is helpful for early diagnosis of IPA and timely medication. And the detection of the GM antigen in BALF and serum serves as a reliable assay for the diagnosis of IPA16. Positive GM test has been taken as an important criterion for the diagnosis of IPA both by the EORTC/MSG and Bulpa criteria. In our report, only four out of nine patients reported positive GM test. So our results showed that GM assay have relatively low sensitivity in nonneutropenic patients, as reported previously 18, 19. Meanwhile, there were other factors affecting result of GM. One of the GM positive patients had been administered piperacillin-tazobactam prior to the test, which was reported to be one of the reasons for false positives in the serum-GM assay20, 21.Some studies have reported that the BALF-GM assay is more sensitive than the serum-GM assay and fungal cultures18, 20, 22. This is a shortcoming that BAL procedure was not conducted through bronchoscope as common in our study. A number of reasons prevented doctors to successfully obtain BALF. First, the bad general condition of patients, extreme discomfort and side effects of bronchoscope reduced patients’ compliance. Second proper standardization techniques of BAL procedure are still lacking. There were variations in the BALF volumes and GM cut-off values reported in different studies. At last the yield of BALF-GM is associated with the lavage site. Therefore, how to accurately locate the lesion is critical yet very difficult.
Previously studies reported that some special signs in CT are highly suggestive of IPA, like cavity, vessel occlusion signs23, patchiness24, airway-invasive features in nonneutropenic cases25. But several papers have reported that CT signs in nonneutropenic IPA is nonspecific. So the imaging findings of nonneutropenic IPA need further study.
First, it is reported that IPA in nonneutropenic patients have different tissue injury pathogenesis compared with neutropenic patients. Berenguer et al reported that nonneutropenic immunocompromised animals revealed a pattern of inflammatory necrosis but no significant angioinvasion, hemorrhage or infarction histologically demonstrated in persistently neutropenic animals with IPA 26. The same tissue injury pattern was found in IPA patients27. It means the nonneutropenic patients should have the corresponding CT scans of tissue necrosis like cavities or halo signs.
Secondly, given IPA was an infectious disease, it might evolve over several phases which might begin with colonization, progress to infection and, finally lead to manifestation of disease symptoms in patients28. This phase evolving was reported in a female case of invasive tracheobronchial Aspergillosis, in which the CT scan was order on day 1, day 4, day 7, day 21, day 63 and day 139. It was found that invasive tracheobronchial Aspergillosis could progress to IPA with extended parenchymal lesions within a short period29. In summary, the CT signs in nonneutropenic IPA might change over time, and specific signs could appear in one certain time point. As showed in our report, IPA underwent a progress beginning with nonspecific CT signs, then developing to cavities within a short period of about 9 days, which was reported as appearing 2 weeks in neutropenic IPA30. Until now, this is the first report about the progress deterioration of CT scans in nonneutropenic IPA, the exact dynamic changes of CT scans in nonneutropenic IPA is far from clear, so specific study designed to observe CT signs at different stages of IPA is warranted.
Right now there are several guidelines of diagnosis and treatment for IPA released by several committees, namely EORTC/ MSG criteria10, Bulpa criteria31 and intensive care unit (ICU) criteria31[32].The scope for each guideline are different. EORTC/ MSG criteria is limited for cancer patients but are also widely used in other patients. The Bulpa criteria is proposed to diagnose IPA specifically in COPD patients. The ICU criteria are proposed to diagnose IPA in the ICU setting. Items required for proven IPA are the same in the three sets of criteria, yet the items required for probable IPA are different. Here we used EORTC/ MSG criteria to diagnose IPA. When patients had a history of severe COPD, Bulpa criteria were also used. As we found, EORTC/ MSG criteria has strict requirements regarding the typical CT findings. So according to EORTC/ MSG criteria, probable/putative IPA should meet one of three CT signs in clinical data as follows, a). Dense, well-circumscribed lesion(s) with or without a halo sign. b) An air-crescent sign. c) A cavity. Yet those typical CT signs for IPA (e.g. halo or air-crescent sign) are particularly rare in early stages in nonneutropenic patient. As showed in our study, the first CT scan only had some nonspecific CT signs as reported before3, 9, 32, which were not helpful for early diagnosis and timely treatment.
Meanwhile, we found there was no requirement for dynamic changes of clinical exacerbation, neither the CT scan nor mycological findings in the EORTC/ MSG criteria. We speculated that it was because of EORTC/ MSG criteria mainly serving for cancer or hematopoietic malignancies, which might deteriorate in hours and days. Yet in IPA in nonneutropenic patients with local airway impaired immunity, the clinical process is not usually so urgent.
Nousheen and colleagues reported the average length of hospital stay were 10.61±9.08 days33, and ours were 45.3 days. We found there was a very significant CT sign deterioration among those patients after average intervals of 9 days, at least 5 days. Our results suggested that EORTC/ MSG criteria were not sensitive enough for nonneutropenic IPA without reexamination of CT scans. Thus, the procedure of applying dynamic monitor of clinical or dynamic CT scans is a way to optimize the EORTC/ MSG criteria.