CT Scan May Help Predict Prognosis of AAV With Lung Involvement
Classifying pulmonary manifestations in people with ANCA-associated vasculitis (AAV) with lung symptoms can help predict disease outcomes and determine which patients should receive more intensive treatment, a study from China suggests.
For example, patients showing bleeding into the lungs (alveolar hemorrhage) in their computed tomography (CT) scan of the chest were at high risk of infection and disease relapse and had some of the worst survival rates, while those with small clumps of immune cells in the lungs (pulmonary granuloma) were likely to experience a relapse but had the best survival rate.
“Therefore, the intensity of immunosuppressive therapy must be carefully valued by considering the baseline CT findings among AAV patients with pulmonary involvement,” the researchers wrote.
The study, “Pulmonary involvement of ANCA-associated vasculitis in adult Chinese patients,” was published in BMC Pulmonary Medicine.
AAV occurs when the immune system turns against the small blood vessels in the body, leading to inflammation and damage. When such inflammation hits the lungs, it may injure the blood vessels surrounding the tiny air sacs responsible for the exchange of gases and nutrients. As a result, there may be respiratory problems, including shortness of breath, chest pain, and coughing up blood.
CT, a procedure in which a computer helps an X-ray machine scan the body to make images of its internal structures, is key for determining pulmonary involvement. While up to 80% of AAV patients show lung abnormalities on a CT scan, “there is still limited information focusing attention on the association between different radiologic patterns and long-term outcomes among AAV patients with pulmonary involvement,” the researchers wrote.
To delve deeper into this, a team of researchers at the Peking University First Hospital, in China, examined the clinical data and CT scans of 366 patients who were diagnosed at their hospital from January 2010 to June 2020 and had pulmonary involvement at diagnosis.
The majority of patients (81.7%) had microscopic polyangiitis, followed by granulomatosis with polyangiitis (16.4%) and eosinophilic granulomatosis with polyangiitis (1.9%). Almost all (97.8%) were positive for ANCA, the autoantibodies that cause most cases of AAV.
The patients were divided into four groups according to the CT images. A total of 55.7% had interstitial lung disease, which causes progressive scarring to the lung tissue; 16.7% had airway involvement (AAV affecting only the trachea and the air passages in the lungs); 14.8% had pulmonary granuloma; and 12.8% had alveolar hemorrhage.
Those with interstitial lung disease were older than patients in the other groups. They also had a higher rate of cardiovascular complications and a lower Birmingham Vasculitis Activity Score (BVAS), meaning less active disease.
Over a median follow-up of 42 months (3.5 years), 27% of the patients had respiratory failure, which occurs when the lungs do not work well enough, and 18% died — most commonly (59.1%) from infections.
When the researchers looked at the rates of survival, they found that patients with interstitial lung disease and alveolar hemorrhage tended to have the poorest prognosis over the years, while those with pulmonary granuloma or airway involvement had better rates of survival.
During the follow-up, 111 (30%) patients experienced a total of 186 relapses, with the first relapse occurring a median of 12 months after diagnosis. The lungs were the most commonly affected organ at the time of relapse, followed by the kidneys.
The proportion of patients who remained relapse-free was higher among those with airway involvement, followed by patients with interstitial lung disease. In contrast, those with alveolar hemorrhage and pulmonary granuloma were more likely to have experienced a relapse.
A total of 237 patients reported 347 infections, with the first infection happening a median of three weeks after diagnosis. The most common was a lung infection, followed by an infection in the genitourinary tract. The most common pathogens were bacteria.
Here, patients with interstitial lung disease were by far those who experienced fewer infections, with over 40% of them remaining free of infections after about 10 years of follow-up. In contrast, all of those with airway involvement had experienced an infection.
“AAV patients with diverse radiological features have different clinical characteristics and outcomes,” the researchers wrote. “Specifically, the [interstitial lung disease] group tends to have a poor long-term prognosis, the [pulmonary granuloma] group is prone to relapse, and the [airway involvement] group is apt to infection.”
Since infections are a common side effect of the immunosuppressive therapies used to manage AAV, “immunosuppressive therapy strategies must keep into account not only AAV activity but patients’ radiological characteristics and their risk of infection as well,” the researchers concluded.