Diagnostic challenges
Aspergillus that has invaded the lung tissue in patients with COVID-19 appears to grow there for some time – around 8-10 days, much longer than in IAPA – before becoming angioinvasive, said Dr. Hoenigl. Such a pathophysiology “implicates that we should try to diagnose it while it’s in the lung tissue, using the BAL fluid, and not yet in the blood,” he said.
Some multicenter studies, including one from Europe on Aspergillus test profiles in critically ill COVID-19 patients, have shown mortality rates of close to 90% in patients with CAPA who have positive serum biomarkers, despite appropriate antifungal therapy. “If diagnosed while confined to the lung, however, mortality rates are more like 40%-50% with antifungal therapy,” Dr. Hoenigl said. (Cohort studies published thus far have fairly consistently reported mortality rates in patients with CAPA greater than 40%, he said.)
Bronchoscopy isn’t always pragmatic or possible, however, and is variably used. Some patients with severe COVID-19 may be too unstable for any invasive procedure, said Dr. Permpalung.
Dr. Permpalung looks for CAPA using serum (1-3) beta-D-glucan (BDG, a generic fungal test not specific to Aspergillus), serum galactomannan (GM, specific for Aspergillus), and respiratory cultures (sputum or endotracheal aspirate if intubated) as initial screening tests in the ICU. If there are concerns for CAPA – based on these tests and/or the clinical picture – “a thoughtful risk-benefit discussion is required to determine if patients would benefit from a bronchoscopy or if we should just start them on empiric antifungal therapy.”
Unfortunately, the sensitivity of serum GM is relatively low in CAPA – lower than with classic invasive aspergillosis in the nonviral setting, sources said. BDG, on the other hand, can be falsely positive in the setting of antimicrobials and within the ICU. And the utility of imaging for CAPA is limited. Both the clinical picture and radiological findings of CAPA have resembled those of severe COVID – with the caveat of cavitary lung lesions visible on imaging.
“Cavities or nodules are a highly suspicious finding that could indicate possible fungal infection,” said pulmonologist Amir A. Zeki, MD, MAS, professor of medicine at the University of California, Davis, and codirector of the UC Davis Asthma Network Clinic, who has cared for patients with CAPA.
Dr. Amir A. Zeki
Cavitation has been described in only a proportion of patients with CAPA, however. So in patients not doing well, “your suspicion has to be raised if you’re not seeing cavities,” he said.
Early in the pandemic, when patients worsened or failed to progress on mechanical ventilation, clinicians at the University of California, Davis, quickly learned not to pin blame too quickly on COVID-19 alone. This remains good advice today, Dr. Zeki said.
“If you have a patient who’s not doing well on a ventilator, not getting better [over weeks], has to be reintubated, has infiltrates or lung nodules that are evolving, or certainly, if they have a cavity, you have to suspect fungal infection,” said Dr. Zeki, who also practices at the Veterans Affairs Medical Center in San Diego. “Think about it for those patients who just aren’t moving forward and are continuing to struggle. Have a high index of suspicion, and consult with your infectious disease colleagues.”
Empiric treatment is warranted in some cases if a patient is doing poorly and suspicion for fungal infection is high based on clinical, radiographic, and/or laboratory evidence, he said.
The CDC’s Dr. Chiller said that screening and diagnostic algorithms currently vary from institution to institution, and that diagnostic challenges likely dissuade clinicians from thinking about fungi. “Clinicians often don’t want to deal with fungi – they’re difficult to diagnose, the treatments are limited and can be toxic. But fungi get pushed back until it’s too late,” he said.
“Fungal diagnostics is an area we all need a lot more help with,” and new diagnostics are in the pipeline, he said. In the meantime, he said, “there are tools out there, and we just need to use them more, and improve how they’re used.”
While reported CAPA thus far has typically occurred in the setting of ICU care and mechanical ventilation, it’s not always the case, Dr. Permpalung said. Lung and other solid organ transplant (SOT) recipients with COVID-19 are developing CAPA and other invasive secondary invasive fungal infections despite not being intubated, he said.
Of 276 SOT recipients with COVID-19 who required inpatient treatment at Johns Hopkins University hospitals from the beginning of the pandemic to March 2022, 23 patients developed invasive fungal infections (13 CAPA). Only a fraction – 38 of the 276 – had been intubated, he said.