Aspergillosis is a fungal disease caused by the fungi of the Aspergillus genus; the burden is underestimated in low-income countries mostly due to the limited laboratory diagnosis capacities. Pulmonary Aspergillosis is one of the common complications of post-tuberculosis lung disease [1]. An estimated 372,000 of patients with post TB sequel subsequently developed chronic pulmonary aspergillosis (CPA). CPA prevalence ranges from less than 1 case per 100,000 population in developed Western European countries and the United States of America to 42.9 cases per 100,000 population in Nigeria and the Democratic Republic of Congo [2]. In Mali, few data have been reported on CPA; a single case of CPA in a patient with a history of tuberculosis has been reported in the medical literature [3]. A one-month (8 December 2016, to 8 January 2017) survey of 380 in- and out-patients at the Pneumo-Phthisiology department of the Point G University Hospital in Bamako identified 7 suspected CPA cases, i.e., a 1.8% frequency [Toloba Y, 2017, unpublished data]. A recent estimation of the burden of fungal diseases has shown an estimated prevalence of 7290 cases of chronic pulmonary aspergillosis (often mistaken for TB), with invasive aspergillosis counting for 1230 cases has been reported [4]. CPA diagnosis is based on a combination of clinical, biological, and radiological findings. Mycological diagnosis is complex and laborious with a risk of releasing false-positive fungi cultured from the environment. Detection of Aspergillus IgG is helpful in the laboratory diagnosis of CPA in patients with post tuberculosis disorders [5]. The measurement of titers of Aspergillus antibodies associated with a fungal ball (aspergilloma) on chest X-ray imaging is sufficient to establish a definitive diagnosis of CPA (simple aspergilloma or chronic cavitary aspergillosis depending on the presence of cavitation) [6]. Aspergillosis disease prevalence in sub-Saharan Africa as well as Aspergillus IgG seroprevalence among at-risk patients are underestimated, likely because very few laboratories are equipped to diagnose the disease, and patient point-of-care diagnosis tools are not implemented. The use of a reliable, rapid, inexpensive and sensitive test [7], such as an LDBio Aspergillus ICT Lateral Flow Assay for IgG and IgM detection would help to diagnose and treat suspected cases of CPA in low-income countries. Pulmonary tuberculosis significantly increases the risk of aspergilloma and other CPA [5]. We conducted a study of at-risk and not-at-risk patients of aspergillosis and compared carriers and non-carriers of Aspergillus IgG/IgM (by ICT and WB) to determine the relationship between the socio-demographic characteristics, clinical phenotypes (chest X-ray sequels) and biological parameters with Aspergillus infection in patients attending the Pneumology-Phthisiology department at the Point G Teaching Hospital in Bamako, Mali.

We enrolled at-risk 50 participants and not-at-risk 50 participants; the predominance of males was observed to be 71 (71%), with a sex ratio of 2.5:1 (M:F) and a mean age of 44.6 (±14) years. Aspergillosis IgG seroprevalence by ICT was 21.4% (21/98) [95% CI, 13.8–30.9], and by WB, it was 21.4% (21/98) for WB [95% CI, 13.8–30.9]. Regarding the agreement between ICT and WB, 21 out of 98 participants were ICT-positive and 21 out of 98 participants were WB-positive (Figure 1).

Twenty participants were concomitantly positive for ICT and WB; therefore, one not-at-risk participant was tested negative for WB and positive for ICT and one not-at-risk participant was positive for WB but negative for ICT. ICT and WB tests could not be performed in two participants among the not-at-risk participants because blood was not collected for one and not tested for one (Figure 2).

The most common features among the at-risk group were male sex, post TB X-ray chest sequels, hemoptysis in former TB patients, Aspergillus spp. growth from sputum, and ICT/WB-positive patients (Table 1).

Aspergillus species identification using MALDI-TOF spectrometry: A. fumigatus was detected in the sputum of 11% of the participants among the at-risk group; 66.6% (2/3) of suspected aspergilloma cases were carrying A. fumigatus. A. flavus was found in 4% of study participants. A. niger, A. nidulans, A. oryzae, A. ochraceus and, A. spinulosporus were found in 1% of participants. A. sydowii was detected in 18% of participants, mainly in the not-at-risk group. Other non-Aspergillus fungal species were grown in 24% of participants’ cultures; mass spectrometry was negative in 22% of cases (Table 2).

Suspected aspergilloma (cavitation + fungal ball with or without positive ICT/WB IgG) was seen in three participants (3%); cured TB patients who had ICT/WB positive represented 12% (Table 3).

Chest X-ray with sequels, hemoptysis and Aspergillus spp. growth from sputum were frequent in Aspergillus IgG antibody carriers. Positive HIV status, asthma, abnormal C-reactive protein and Chronic obstructive pulmonary disease (COPD) were not associated with Aspergillus IgG (Table 4).

Chest X-ray sequel characteristics among participants were pulmonary cavitation with a fungal ball identified in three participants, confirming a suspected aspergilloma. Aspergillus IgG was detected in two suspected aspergilloma. Fibrotic destruction was seen in 16.3%, nodules in 38.7%, variable pulmonary sequels in 63.2%, and radiological progression in 4.08% (Table 5). Participants with suspected CPA are also those who had fibrotic destruction and radiological variable sequels (Table 5).

This study is pioneering in its investigation of aspergillosis seroprevalence in patients who are at risk of and not at risk of aspergillosis in a hospital setting in Mali. The seroprevalence of Aspergillus IgG and prevalence of CPA were studied in different population subgroups and settings using qualitative and quantitative tests [11,12,13]. The prevalence of suspected cases of CPA (aspergilloma) and the seroprevalence of Aspergillus IgG among study participants would indicate that Aspergillus infection is common in Malian adult patients, as suggested by Niaré-Doumbo et al. [4]. As previously published [9,14], we found a substantial agreement between ICT and WB results. The overall prevalence of suspected (possible) aspergilloma in our post TB patients with chest X-ray sequels (pulmonary cavities) matched previously reported cases; CPA was reported to develop commonly in post TB pulmonary cavitation [15], which is the common post pulmonary TB sequel [16]. Therefore, other post TB pulmonary sequels, such as fibrotic destruction and variable radiological sequels were found to be associated with Aspergillus IgG/IgM in our study; these chest radiography characteristics are recognized among the imaging spectrum of CPA [17]. In Seoul, South Korea [18], 2.9% of the 345 patients diagnosed, treated, and followed-up until TB was cured developed chronic pulmonary aspergillosis. The prevalence of aspergilloma was higher in patients with a history of treatment of pulmonary TB [19]. CPA may develop in newly diagnosed pulmonary TB patients at diagnosis and during anti-tubercular treatment, with increasing CPA prevalence during the treatment course [20]. In our study, Aspergillus IgG seroprevalence was two-fold higher in at-risk participants than in not-at-risk participants. This result highlights that exposition to Aspergillus spp. infection is high and the risk of infection increases in patients with post TB disorders in low-income countries. Similar variations in Aspergillosis IgG seroprevalence among healthy volunteers, TB close contacts, active TB patients and old TB cases with 33.0% (66/200), 37.7% (123/326), 26.5% (139/524) and 43.2% (83/192), respectively, were found by Lee et al. in 2020 in Taiwan using ImmunoCAP^TM system [12]. Considering the seroprevalence of Aspergillus IgG among our study patients with post TB chest X-ray sequels, we assume both tests evaluated in our study could be useful for suspected CPA screening in high-TB-endemic, low-income countries such as Mali. The difference observed between both studies could be linked to the sensitivity of the ImmunoCAP^TM system, post TB prevalence, and the criteria used to enroll at-risk participants in our study.

Men were more frequently enrolled than women in both groups; this could explain why men were carrying more Aspergillus IgG than women; male predominance has been reported by several authors [7,11].

A study conducted in Mozambique in individuals treated for and cured from tuberculosis showed that 3 out of 61 (5%) had Aspergillus-specific IgG detected using automated Immunocapture^® (Phadia 100, Thermo Fisher Scientific, Uppsala, Sweden); the HIV-positive patients included in this study had no detectable levels of anti-Aspergillus antibodies [11]. Our findings are consistent with the Mozambican study; in the present study, for both ICT and WB, HIV-positive patients were Aspergillus IgG-negative. The use of ICT/WB may not be helpful to screen aspergillosis in HIV-positive patients with post TB chest radiography abnormalities.

Aspergillus spp. are frequently identified in samples collected in confirmed CPA cases, Hunter et al. found 36% carriers of A. fumigatus among confirmed CPA cases [7]. The growth of Aspergillus spp. in patients’ sputum with chest radiography sequels associated with the Aspergillus IgM (LDBio IgG/IgM positive) in the present study can confirm active Aspergillus infection, as more than half of the suspected aspergilloma cases had A. fumigatus isolated from culture.

Niaré-Doumbo et al. found A. fumigatus in 3% of cases, and A. niger was the predominant species (29%) in the sputum and the nasal swabs from inpatients at the oncology-hematology department in Point G Teaching Hospital [4]; this result is not consistent with what we found because the characteristics of our patients’ illnesses were different from those from Niaré-Doumbo et al.’s study. Hunter et al. reported A. fumigatus as the most prevalent species in CPA patients [7], and this finding is consistent with what we found in the current study. Variation in Aspergillus species circulating in hospital wards and their frequency could be dependent on inpatients’ disorders instead of ward characteristics.

One study limitation is the lack of confirmation of CPA diagnosis using antibody titer measurements; therefore, the at-risk participants with chest X-ray abnormalities associated with Aspergillus IgG/IgM using ICT test strips and immunoblot assays could be considered as possible CPA. An assessment of IgG titers is needed for the confirmation of suspected cases.

Our findings suggest that anti-Aspergillus fumigatus IgG/IgM carriage is common in post-TB patients in Mali. The detection of anti-Aspergillus antibodies using ICT is well adapted to laboratories with limited resources in highly exposed patients in endemic TB countries. Our findings advocate for making this diagnostic test available in low-income countries such as Mali to enhance the screening of aspergillosis, a life-threatening disease. Confirmation tests determining antibody titers should be implemented for the purpose of CPA diagnosis and treatment.