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Sci Rep
Sci Rep
Scientific Reports
2045-2322
Nature Publishing Group UK London

39223294
71455
10.1038/s41598-024-71455-7
Article
Investigation of risk factors for invasive pulmonary aspergillosis among patients with COVID-19
Song Li 1
Qiu Ling 2
Wang Gang 1
Zou Wenlu 1
Zhang Shilong 34
http://orcid.org/0000-0003-0377-6667
Sai Lintao sailintao@sdu.edu.cn

1
1 https://ror.org/056ef9489 grid.452402.5 0000 0004 1808 3430 Department of Infectious Diseases, Qilu Hospital of Shandong University, Wenhua Xi Road 107, Jinan, 250012 Shandong China
2 Department of Infectious Diseases, Shandong Provincial Public Health Clinical Center, Lieshishan Dong Road 11, Jinan, 250102 Shandong China
3 https://ror.org/0207yh398 grid.27255.37 0000 0004 1761 1174 Center for Health Management and Policy Research, School of Public Health, Cheeloo College of Medicine, Shandong University, Wenhua Xi Road 44, Jinan, 250012 Shandong China
4 https://ror.org/0207yh398 grid.27255.37 0000 0004 1761 1174 NHC Key Laboratory of Health Economics and Policy Research, Shandong University, Wenhua Xi Road 44, Jinan, 250012 Shandong China
2 9 2024
2 9 2024
2024
14 2036431 10 2023
28 8 2024
© The Author(s) 2024
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
COVID-19 associated pulmonary aspergillosis (CAPA) had been reported, and raised concern about this secondary infection due to the high mortality. This study aimed to investigate the risk factors for CAPA. The enrolled 114 COVID-19 patients were further divided into CAPA group and non-CAPA group. Demographic characteristics, underlying diseases, laboratory parameters and therapeutic schedule between the two groups were compared to identify the independent risk factors for CAPA by univariate analysis and multivariable logistic regression analysis. Sensitivity and specificity of independent risk factors were confirmed by receiver operating characteristic (ROC) curve analysis. Univariate analysis showed that renal transplant, IL-6 and CRP levels, decreased CD4 + T cell and CD8 + T cell, duration of antibiotics therapy, and prolonged mechanical ventilation were risk factors for development of CAPA. These factors were further analyzed by multivariable logistic regression analysis and the results indicated that elevated IL-6 level, decreased CD4 + T cell and prolonged mechanical ventilation could be recognized as independent risk factors for CAPA in COVID-19 patients. Identification of these risk factors is essential to initiate antifungal therapy as soon as possible to improve outcome of patients with CAPA.

Keywords

SARS-CoV-2
Aspergillus
COVID-19 associated invasive pulmonary aspergillosis
Risk factors
Subject terms

Fungal infection
Viral infection
Risk factors
issue-copyright-statement© Springer Nature Limited 2024
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pmcIntroduction

Aspergillus, as an opportunistic pathogenic fungi, usually causes life-threatening infection in immunocompromised patients. Invasive pulmonary aspergillosis (IPA) is one of the most common type of Aspergillus infections, which is usually described in patients with hematological malignancies (especially with persistent neutropenia), allogeneic hematopoietic stem cell transplant (HSCT), solid organ transplant (SOT) or prolonged corticosteroid use. In addition, severe viral lower respiratory infection had been also recognized as a risk factor for IPA1. Such as Influenza virus, influenza associated pulmonary aspergillosis (IAPA) had been considered a severe complication among influenza patients and increased influenza associated mortality2,3. Similarly, patients with severe COVID-19 are at high risk of developing IPA1.

COVID-19 caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an emerging respiratory infectious disease and was designated as a pandemic on 11 March 2020 by WHO. With the expansion of COVID-19 epidemic, more cases diagnosed as COVID-19 associated pulmonary aspergillosis (CAPA) had been reported, which raised concern about this secondary infection due to the high mortality (up to about 50%)4,5. However, the reasons for increasing the susceptibility of COVID-19 patients to Aspergillus are complex and diverse. Lung epithelium undergoes disruptive change over the course of severe SARS-CoV-2 infection, including tissue disruption that facilitates secondary Aspergillus invasion and exposure of receptors to which Aspergillus can adhere6,7. In addition, Aspergillus spores themselves release molecules (such as proteases) with the potential to increase permeability and tissue damage7. Other risk factors are also involved, including underlying diseases (such as diabetes), undergoing invasive medical procedures, overuse of corticosteroids and broad-spectrum antibiotics, and prior or newly acquired immune dysfunction8–13. However, limited systematic studies on the exact relationship between these risk factors and CAPA were performed.

The reported incidences of CAPA varied by regions. Some investigations in Europe had reported that incidences ranged from 14.1 to 33.3%5,14–16. Several studies from China had reported the incidence of CAPA during the initial wave of COVID-19, ranging from 1 to 42.1%6,9,17–19. The different estimates of CAPA incidence maybe due to the difference in criteria for CAPA definition. Most early studies adopted the diagnostic criteria of IPA from the 2019 European Organization for the Research and Treatment of Cancer/Mycosis Study Group (EORTC/MSG) consensus, in which high-risk host factors were important consideration20. However, many patients with CAPA do not have classical host risk. To standardize clinical researches and clinical management of CAPA, the European Confederation for Medical Mycology and the International Society for Human and Animal Mycology (ECMM/ISHAM) formulated consensus criteria for defining and managing CAPA21.

COVID-19 pandemic has been associated with an increase in the incidence of IPA. Since the high mortality rate of CAPA, it is significant to raise awareness of the importance of early identification of CAPA. The aim of this retrospective study was to investigate and summarize the risk factors for IPA among COVID-19 patients, which could help physicians to be more alert to the occurrence of CAPA.

Materials and methods

Study design

This was a monocentric retrospective study. The enrolled patients were adults, who admitted to Qilu Hospital of Shandong University (one of the largest tertiary hospitals in Shandong province) for COVID-19 between 25 December 2022 and 28 February 2023. COVID-19 patients were confirmed by testing RNA of SARS-CoV-2 from nasopharyngeal swab and respiratory samples through RT-PCR assay. During the period of this study, Omicron variant was the only prevalent strain (including BA.5.2 and BF.7.14 subtypes). The enrolled patients were from departments of Emergency, Infectious Diseases, Respiratory Medicine and Intensive Care Unit (ICU).

This study was approved by the Ethics Committee on Scientific Research of Shandong University Qilu Hospital (KYLL-2017612). Written informed consent was waived by the Ethics Committee on Scientific Research of Shandong University Qilu Hospital due to the retrospective observational nature of our study. Furthermore, all methods were performed in accordance with the Declaration of Helsinki and the relevant guidelines and regulations.

CAPA definition and data collection

The definition of CAPA in our study was made retrospectively followed the ECMM/ISHAM consensus criteria21, in which CAPA was proposed to be defined as proven, probable and possible on the basis of sample validity, imaging features and clinical manifestations. All authors from this study had jointly learned this consensus and reached a consensus on the diagnostic criteria for CAPA. On this basis, one author was assigned to complete the CAPA diagnosis of COVID-19 patients. The enrolled COVID-19 patients were further divided into CAPA group and non-CAPA group.

Related data on enrolled COVID-19 patients were collected and recorded according to their electronic medical records, including demographic characteristics, underlying diseases, laboratory parameters and therapeutic schedule. Comparison of these data between CAPA group and non-CAPA group was performed to investigate and summarize the risk factors for CAPA.

Statistical analyses

All statistical analyses were conducted using SPSS 26.0 (SPSS software, NY, USA). The count data were represented by rate and compared by Chi-square test or Fisher exact probability test. The measurement data were confirmed as abnormal distribution data by normality test. Then, the measurement data of abnormal distribution were expressed as median (interquartile) and compared by the Spearman’s rank coefficient of correlation. Factors with P < 0.05 in univariate analysis were further analyzed using multivariable logistic regression analysis to identify the independent risk factors for CAPA. Independent risk factors were analyzed by receiver operating characteristic (ROC) curve analysis to evaluate the sensitivity and specificity to predict CAPA. For all statistical analyses, a P-value less than 0.05 was considered statistically significant.

Results

The observational study was from one centre in Shandong province (China) to identify risk factors for CAPA between 25 December 2022 and 28 February 2023, when COVID-19 became a pandemic in China. A total of 114 laboratory-confirmed COVID-19 patients were enrolled. 38 patients (33.3%) were diagnosed with CAPA based on the definition criteria from the ECMM/ISHAM consensus, and then were assigned to the CAPA group. Among patients with CAPA, there were one proven patient (2.6%), twenty-seven probable patients (71.1%) and ten possible patients (26.3%).

Average age of the enrolled patients was 70.5 (± 14.3) years old, and 80 patients (70.2%) were male. Either in CAPA group or in non-CAPA group, more male patients were found than female patients (73.7% vs 26.9% and 68.4% vs 31.6%, respectively). However, there was no statistically significant difference in gender between the two groups (P = 0.563). Advanced age is a high-risk factor for progression to severe COVID-19, therefore age was analyzed to assess whether it was a risk factor for CAPA. As shown in Table 1, patients in CAPA group and non-CAPA group were further divided into two age groups, respectively. Patients older than 65 years accounted for 71.1% (27/38) and that younger than 65 years accounted for 28.9% (11/38) in CAPA group. In non-CAPA group, patients older than 65 years and younger than 65 years accounted for 75.0% (57/76) and 25.0% (19/76), respectively. The difference in age composition was not statistically significant (P = 0.652). Obesity is another high-risk factor for progression to severe COVID-19. The enrolled COVID-19 patients were divided into three group based on their Body Mass Index (BMI, shown in Table 1). The proportion of overweight patients was similar between CAPA group and non-CAPA group (39.5% vs 35.5%), and the difference of BMI between the two groups was not statistically significant (P = 0.877).Table 1 Comparison of demographic characteristics and underlying diseases of patients between CAPA group and non-CAPA group.

Variables	All patients (N = 114)	CAPA group (N = 38)	non-CAPA group (N = 76)	x2	P	
Age (years)	
 ≥ 65	84 (73.7%)	27 (71.1%)	57 (75.0%)	0.204	0.652	
 < 65	30 (26.3%)	11 (28.9%)	19 (25.0%)	
Gender	
 Male	80 (70.2%)	28 (73.7%)	52 (68.4%)	0.335	0.563	
 Female	34 (29.8%)	10 (26.9%)	24 (31.6%)	
BMI	
 < 18.5	4 (3.5%)	1 (2.6%)	3 (3.9%)	0.262	0.877	
 ≥ 18.5, < 25	68 (59.6%)	22 (57.9%)	46 (60.5%)	
 ≥ 25	42 (36.8%)	15 (39.5%)	27 (35.5%)	
Diabetes	34 (29.8%)	13 (34.2%)	21 (27.6%)	0.524	0.469	
COPD	19 (16.7%)	8 (21.1%)	11 (14.5%)	0.789	0.374	
Solid tumor	17 (14.9%)	6 (15.8%)	11 (14.5%)	0.035	0.853	
Renal transplant	9 (7.9%)	7 (18.4%)	2 (2.6%)	6.650	0.010	

Associated underlying diseases, including diabetes, chronic obstructive pulmonary disease (COPD), solid tumor and renal transplant, were included in the analysis of risk factors for CAPA (shown in Table 1). Although the incidences of diabetes, COPD and solid tumor in CAPA group was slightly higher than that in non-CAPA group, the differences was not significant (P = 0.469, P = 0.853 and P = 0.374, respectively). A total of nine patients (7.9%) were in the post-renal-transplant status, and all of them were taking tacrolimus and mycophenolate mofetil to prevent immune rejection. The proportion of renal transplant among patients in CAPA group was significantly higher than that in non-CAPA group (18.4% vs 2.6%). A statistically significant difference between the two groups was observed (P = 0.010), which suggested that renal transplant with immunosuppressive therapy might be a potential risk factor for CAPA.

SARS-CoV-2 infection can lead to inflammatory response, and interleukin 6 (IL-6) and C-reactive protein (CRP) are usually used to evaluate the intensity of this response in clinical practice. Strong inflammatory response lead to impairment of immune function, and opportunistic Aspergillus infection is prone to occur. In our study, level of IL-6 and CRP were observed and compared between CAPA group and non-CAPA group to assess the significance of the difference. As shown in Table 2, the median level of IL-6 and CRP in CAPA group were higher than that in non-CAPA group, which suggested that stronger immune response was produced among patients with CAPA. The differences of level of IL-6 and CRP between the two groups were statistically significant (P < 0.001 and P < 0.001).Table 2 Comparison of laboratory parameters and therapeutic schedule of patients between CAPA group and non-CAPA group.

Variables	All patients
Median (interquartile)	CAPA group
Median (interquartile)	non-CPAP group
Median (interquartile)	P	
IL-6 (mmol/L)	29.59 (6.69–150.09)	275.15 (63.21–842.23)	14.22 (3.26–39.95)	 < 0.001	
CRP (mmol/L)	43.35 (15.26–118.35)	118.85 (42.69–193.39)	32.65 (9.97–67.67)	 < 0.001	
CD4 + T cell (cells/μl)	254 (137–424)	135 (62–215)	353 (202–523)	 < 0.001	
CD8 + T cell (cells/μl)	142 (77–280)	62 (26–119)	206.5 (110–311)	 < 0.001	
B cell (cells/μl)	123 (65–210)	108 (52–167)	134 (76–218)	0.106	
Dexamethasone dose (mg)	6 (5.00–7.50)	6.00 (5.00–7.50)	6.00 (5.00–7.50)	0.227	
Duration of dexamethasone therapy (d)	6 (3–9)	5.5 (3–8)	6.5 (4–9)	0.293	
Duration of antibiotics therapy (d)	7 (2–12)	8 (4–12)	5.5 (0–12)	0.044	
Duration of mechanical-ventilation (d)	0 (0–6)	7 (0–11)	0 (0–4)	 < 0.001	

Reduction in the count of lymphocyte is one of the characteristics of SARS-CoV-2 infection leading to weaken the ability against opportunistic Aspergillus infection. CD4+ T cell, CD8+ T cell and B cell were compared to assess the relationship between the counts and CAPA. As shown in Table 2, the median counts of CD4+ T cell and CD8+ T cell in CAPA group were less than that in non-CAPA group, and the differences were statistically significant (P < 0.001 and P < 0.001). However, the counts of B cell were similar between the two groups and the difference was not significant (P = 0.106).

In addition, some therapeutic interventions including dose of dexamethasone, duration of dexamethasone therapy, duration of broad-spectrum antibiotics therapy and duration of mechanical-ventilation were compared between the two groups. The results were shown in Table 2. The dose and duration of dexamethasone therapy were not statistically significant between the two groups (P = 0.227 and P = 0.293). However, the duration of broad-spectrum antibiotics therapy and mechanical-ventilation were longer in CAPA group than that in non-CAPA group, and the differences were statistically significant (P = 0.044 and P < 0.001).

Seven potential risk factors for CAPA were found by univariate analysis, which were further analyzed through multivariable logistic regression analysis to identify independent risk factors. As shown in Table 3, the results indicated the level of IL-6, counts of CD4+ T cell and duration of mechanical-ventilation were associated with independent occurrence risk for CAPA (P = 0.023, P = 0.011 and P = 0.023). For level of IL-6 and counts of CD4+ T cell, receiver operating characteristic (ROC) curve analysis was performed to evaluate the sensitivity and specificity for predicting CAPA. Cut-off value of IL-6 to predict CAPA was 63.19 pg/ml (Roche Diagnostics GmbH, Mannheim, Germany; reference range 0–7 pg/ml), with sensitivity of 76% and specificity of 87%. Cut-off value of CD4+ T cell counts to predict CAPA was 196/μl (Becton, Dickinson and Company, NJ, USA; reference range 441–2156 cells/μl), with sensitivity of 74% and specificity of 79% (shown in Table 4 and Fig. 1).Table 3 Multivariable logistic regression analysis for risk factors of CAPA.

Variables	B	SE	Wals	P	OR	95% CI	
Renal transplant (%)	− 2.027	1.203	2.840	0.092	0.132	0.012–1.392	
Duration of antibiotics therapy (d)	− 0.069	0.057	1.462	0.227	0.934	0.836–1.043	
Duration of mechanical-ventilation (d)	0.182	0.075	5.875	0.015	1.199	1.035–1.389	
IL-6 (pg/ml)	0.004	0.002	5.191	0.023	1.004	1.001–1.007	
CRP (mmol/L)	0.004	0.005	0.551	0.458	1.004	0.993–1.015	
CD4 + T cell (cells/μl)	− 0.007	0.003	6.454	0.011	0.993	0.988–0.998	
CD8 + T cell (cells/μl)	0.001	0.003	0.101	0.751	1.001	0.996–1.006	

Table 4 Receiver operating characteristic curve analysis of independent risk factors for CAPA in COVID-19 patients.

Parameters	Cutoff value	Area under curve (95%CI)	Sensitivity (%)	Specificity (%)	
IL-6 (pg/ml)	63.19	0.873 (0.802–0.943)	76	87	
CD4 + T cell (cells/μl)	196	0.820 (0.740–0.900)	74	79	

Fig. 1 Receiver operating characteristic (ROC) curve analysis of predictors for CAPA. (a) ROC curve of IL-6 (Cutoff value: 63.19; Area under curve: 0.873; 95% CI: 0.802–0.943; Sensitivity: 76.0%; Specificity: 87.0%); (b) ROC curve of CD4+ T cell (Cutoff value: 196; Area under curve: 0.820; 95% CI: 0.740–0.900; Sensitivity: 74.0%; Specificity: 79.0%).

Discussion

Although COVID-19 has been removed from the list of emergency public health events in May 2023 by WHO, SARS-CoV-2 will coexist with humans for a long time. When we take more attention to health effects from long COVID, secondary infection occurring in the acute phase of COVID-19 should also be emphasized. COVID-19 had been reported to be associated with increasing occurrence of invasive fungal coinfection (mainly including aspergillosis, candidaemia and mucormycosis) in the beginning of pandemic6,10,12, and since then, COVID-19 associated invasive fungal infection was widely recognized. COVID-19-associated pulmonary aspergillosis (CAPA), which may exacerbate COVID-19 severity, compromise therapeutic efficacy and increase mortality, is the most concerned category and continues to be frequently described with review, case report/series, control studied, and cohort studies5,22. Therefore, early identification and intervention are important to improve the prognosis of patients with CAPA. This observational study was performed to identify risk factors for CAPA during the largest epidemic of COVID-19 in China between 25 December 2022 and 28 February 2023.

Analysis of risk relationship indicated that age was not a high risk factor for CAPA in our study, which might be associated with the age composition of the two groups. The study was conducted during the largest epidemic of COVID-19 in China, and medical resources were relatively scarce. Advanced age is a high-risk factor for progression to severe COVID-19 and elderly patients were given priority for admission. Therefore, the proportion of patients older than 65 years old was similar between the CAPA group and non-CAPA group in this study. Obesity is another high-risk factor for progression to severe COVID-19. Body Mass Index (BMI) was used to stratify the degree of obesity. Although the proportion of patients with BMI ≥ 25 was higher in CAPA group than that in non-CAPA group, the difference was not statistically significant. Thus, obesity also can not be considered a high-risk factor for CAPA.

Such underlying diseases, including diabetes, chronic respiratory diseases, solid tumor and solid organ transplant, predispose to invasive fugal disease, particularly when treatments of these diseases already involve immunosuppressive therapy or the conditions are poorly controlled. In the present study, diabetes, chronic obstructive pulmonary disease (COPD), solid tumor (located in liver, kidney and lung) and renal transplant were analyzed to confirm the risk relationship with CAPA. Only renal transplant was statistically significant in univariate analysis, and none of them could be considered an independent risk factor for CAPA by multivariable logistic regression analysis. Diabetes is a well-established risk factor for the development of invasive fungal diseases. Dimitrios23 had reported that approximately 39% of the patients with mucormycosis and 21% of the patients with invasive aspergillosis had diabetes. In our study, approximately 34.2% of enrolled patients with invasive pulmonary aspergillosis had underlying diabetes, meanwhile 27.6% patients in non-CAPA group had underlying diabetes. Poor control of blood glucose is an important prerequisite for invasive fungal infection among COVID-19 patients with diabetes. For example, COVID-19 associated mucormycosis (CAM) in India, a certain risk factor was related to the poorly controlled diabetes24. The result from our study suggested that underlying diabetes was not associated with the occurrence of CAPA, which might benefit from well-controlled blood glucose level. Patients with malignant tumors who are receiving chemotherapy or radiotherapy are often in a state of immunosuppression, which is a high risk factor for fungal infection. However, this association was not present in our study. A possible explanation was that patients with these solid tumors were in a stable stage of their condition, rather than undergoing chemotherapy or radiation therapy. Contrary to the situation of solid tumor patients, all patients with renal transplant in our study were taking tacrolimus and mycophenolate mofetil to avoid immune rejection, which made patients more prone to fungal infections. However, renal transplant was not confirmed to be an independent risk factor for CAPA by multivariable logistic regression analysis. However, it should be noted that the small sample size and low proportion of these comorbidities in our single center might affect the determination of the association with CAPA, which could be revealed in larger studies13.

On infection, SARS-CoV-2 binds to angiotensin converting enzyme 2 (ACE-2) receptors located on alveolar epithelial cells leading to damage of integrity of the epithelial barrier and local innate immune function25. Viruses enter epithelial cells and begin to replicate that instigates an imbalanced pro-inflammatory immune response and activates the innate and adaptive immune systems leading to up-regulate the expression of cytokines, including IL-626,27. The excessive inflammation response further aggravates the damage of immune function, which makes COVID-19 patients more susceptible to invasive fungal infection. IL-6, as an important member of the cytokines network, is a multifunctional cytokine and plays a central role in acute inflammation in COVID-19 patients28. The level of IL-6 indicates the intensity of the inflammation response. Therefore, we analyzed level of IL-6 to assess the risk relationship with CAPA. The result of multivariable logistic regression analysis suggested that elevated level of IL-6 could be considered an independent risk factor for development of CAPA. In order to more accurately evaluate the relationship, ROC curve analysis was performed to confirm a best cutoff value. The result suggested that the sensitivity and specificity for predicting CAPA were higher when the level of IL-6 was 63.19 pg/ml.

Lymphocytes in COVID-19 patients often show a hyperactive and were exhausted25. Therefore, lymphopenia is a common complication in COVID-19 patients, and has been already considered a risk factor for COVID-19 associated invasive aspergillosis, mucormycosis and Pneumocystitis carinii pneumonia (PCP)26,29,30. Decrease in CD4+ T cells and CD8+ T cells were observed in COVID-19 patients by peripheral flow cytometry analysis31. Generally, cell mediated immune response plays powerful roles in protection against invasive fungal infection. CD4+ T cell (antigen presenting cell) and CD8+ T cell (cytotoxic cell) constitute an important immune defense barrier against fungal infection. In the present study, CD4+ T cells and CD8+ T cells decreased significantly in CAPA group. These decreased T cells resulted in the number of active T cells were insufficient to participate in cell mediated immune response and caused lower cellular immune function, which increased the risk of CAPA. Although the decrease in CD4+ T cells and CD8+ T cells was associated with CAPA by univariate analysis, only the decline of CD4+ T cell was considered an independent risk factor for CAPA by multivariable logistic regression analysis. And base on the ROC curve analysis, the sensitivity and specificity for predicting CAPA were higher when the counts of CD4+ T cell < 196/μl.

Systemic inflammatory response is common among COVID-19 patients, which can lead to multisystem organ dysfunction including lung injury. In order to mitigate the damage caused by inflammatory response, systemic corticosteroid therapy are recommended for patients with COVID-19 who require supplemental oxygen32. However, use of corticosteroid might hamper patients’ immune responses and clearance of pathogens, which would increase their susceptibility to invasive fungal infection. Questions regarding the possible relationship between corticosteroid use and the occurrence of invasive fungal infection in COVID-19 patients was accompanied by the use of corticosteroid for managing COVID-19 patients33. A prospective study showed that the use of high-dose systemic corticosteroid was signifificantly associated with developing aspergillosis in COVID-19 patients14. Another cohort study from Brazil showed that a tenfold increase in candidemia was observed among severe COVID-19 patients who received high-dose corticosteroid34. However, it must be noted that high-dose corticosteroid was used in these studies and then invasive fugal infection developed14,34,35. Appropriate dose and duration of corticosteroid are recommended for managing COVID-19 patients36. We strictly followed the recommendation from the treatment guidelines for use of corticosteroid to manage COVID-19 patients, which might explain that the dose and duration of dexamethasone therapy were not associated with CAPA in our study.

Severe SARS-CoV-2 infection leads to extensive alveolar damage, which will cause acute respiratory distress syndrome (ARDS). Patients with severe ARDS require assisted mechanical ventilation to compensate for respiratory function. However mechanical ventilation exposes the patient to fungal colonization and invasive fungal disease37. Therefore, mechanical ventilation and the duration of ventilation are considered risk factors for CAPA among patients in the ICU33,38. Similar finding was seen in our study, in which duration of mechanical-ventilation in CAPA group was significant longer than that in non-CAPA group. On multivariate analysis, long-term mechanical ventilation was recognized as an independent risk factor for CAPA.

Conclusion

CAPA mainly occurs in severe COVID-19 patients, and the incidence varies in different countries. The overall mortality of patients with CAPA were from 43% to 71.4%, which was significant higher than that in patients without CAPA39,40. Previous studies have shown that anti-Aspergillus treatment is closely related to the mortality of patients with CAPA. Mortality of CAPA patients without anti-Aspergillus treatment ranged from 59 to 90%, whereas mortality ranged from 38% to 66.7% among CAPA patients who had received anti-Aspergillus treatment41,42. In view of the high morbidity and mortality of CAPA, early identification and initiation of anti-Aspergillus treatment are important to reduce the mortality of CAPA patients. In this study, prolonged mechanical ventilation, elevated IL-6 level and decreased CD4+ T cell could be recognized as independent risk factors for CAPA. Identification of these risk factors is essential to initiate antifungal therapy as soon as possible to improve outcome of patients with CAPA.

Acknowledgements

We thank to the colleagues in the department of infectious disease and department of clinical laboratory for their support of this study.

Author contributions

S.Lt. and S.L. contributed to the study conception and design. Material preparation, data collection and analysis were performed by S.L., Q.L., W.G., Z.W. and Z.S.. The first draft of the manuscript was written by S.L. and Q.L.. S.Lt. revised the draft. All authors commented on previous versions of the manuscript, and approved the final manuscript.

Data availability

The databases used and analyzed during the current study are available from the corresponding author on reasonable request.

Competing interests

The authors declare no competing interests.

Publisher's note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

These authors contributed equally: Li Song and Ling Qiu.
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