by every 8 weeks for one year. this allows for a determination of baseline ige levels, though it's important to note that most patients do not entirely reduce ige levels to baseline. chest x-ray or ct scans are performed after 1–2 months of treatment to ensure infiltrates are resolving. epidemiology there are limited national and international studies into the burden of abpa, made more difficult by a non-standardized diagnostic criteria. estimates of between 0.5 and 3.5% have been made for abpa burden in asthma, and 1–17.7% in cf. five national cohorts, detecting abpa prevalence in asthma (based on gina estimates), were used in a recent meta-analysis to produce an estimate of the global burden of abpa complicating asthma. from 193 million people with asthma worldwide, abpa prevalence in asthma is estimated to be between 1.35 and 6.77 million people, using 0.7–3.5% attrition rates. a compromise at 2.5% attrition has also been proposed, placing global burden at around 4.8 million people affected. the eastern mediterranean region had the lowest estimated prevalence, with a predicted case burden of 351,000; collectively, the americas had the highest predicted burden at 1,461,000 cases. these are likely underestimates of total prevalence, given the exclusion of cf patients and children from the study, as well as diagnostic testing being limited in less developed regions.