Our study investigated the clinical characteristics and etiology of non-CF bronchiectasis in a cohort of patients followed up in a tertiary care hospital in the Middle East. There was a predominance of female patients in the studied cohort, which is in keeping with most of the published data (11). The median age of our cohort was 58 years of age. It is noteworthy that several previous studies have shown increasing prevalence of bronchiectasis in older adults (12, 13). The median age of general population in Abu Dhabi is only 32 years (14) which is significancy younger than most developed countries. It is thus likely that as the population gradually ages, the prevalence of bronchiectasis will also increase. The BSI is a validated clinical prognostication tool, used to risk stratify patients with bronchiectasis, with higher BSI score being associated with higher mortality (13). In our study, the calculated BSI was mild in 28%, moderate in 27% and severe in 45% of the cohort. Age is an important prognostic factor in patients with bronchiectasis with older patients having more symptoms and hence, age is one of the components that make up the BSI (13) however we were not did not find a significant correlation between age and FEV1 in our patient group.
The predominant spirometry pattern in our cohort was obstructive which was also associated with worse clinical outcome. We found patients with obstructive spirometry had significantly higher mean BSI (10.1 vs 6.9) compared to patients with restrictive spirometry. In addition, eight out of the 11 deceased patients in our cohort had obstructive spirometry. These findings are compatible with what is described in the literature previously (15).
There are well documented geographic variations in the prevalence of various aetiologies of bronchiectasis (3). In our study, the most common etiology was post infectious (excluding post TB). When added together, post infectious and post tuberculosis cases accounted for 35% of patients. The second commonest etiology in our cohort were those labelled as idiopathic, while PCD was the fourth most common cause found in our cohort. The post-infectious and idiopathic aetiologies are common in Asian patients as shown in a recent study from Taiwan which found post infectious and in particular post-tuberculosis as the most common etiology (16). However, PCD as the third most common etiology in our cohort is somewhat unusual and needs more explanation. In a previous French study of inherited factors for diffuse bronchiectasis in adults, PCD was determined as the etiology in 13% of the study population, however that cohort only had 38 patients with diffuse bronchiectasis, with 5 patients having a diagnosis of PCD. Four out of the 5 patients with PCD diagnosis in this study were of African descent (17). A paediatric study form India (n:80) reported suspected PCD in 15% of study participants(18). Most other larger studies of bronchiectasis have shown much lower prevalence of PCD(3) and it is possible to deduce form available data that prevalence of PCD may be higher in the non-Caucasian populations. This observation is further supported by the results from our cohort. Furthermore, the higher prevalence of PCD in our study may be explained by several other factors which include a higher proportion of younger patients, high rates of consanguinity in the region and the fact that our hospital is the main referral centre in the country for complex bronchiectasis patients.
In our study Pseudomonas aeruginosa (32%), Hemophilus influenzae (9%) and MSSA (7%) were the pathogens most commonly isolated. Only three patients had NTM (1.2%) colonization in sputum. Previous studies have reported major geographic variations in microbiology (3) but pseudomonas predominance in our cohort is in keeping with prior published data. The incidence of TB and NTM are known to be inversely related (19), probably due to cross-immunity, and high endemicity of TB in UAE probably accounts for low NTM rates in our study population.
Bronchiectasis is a common chronic lung disease and is the main cause of mortality and morbidity in patients with primary or secondary antibody-deficiencies(20, 21). It is also the most commonly reported post-infectious complication in both paediatric-onset and adult‐onset common variable immunodeficiencies(22). However, immunodeficiency is a treatable cause of bronchiectasis if diagnosed and treated early with immunoglobulin replacement therapies (either intravenously or subcutaneously). Patients with bronchiectasis and immunodeficiency may benefit from a higher dose of immunoglobulin replacement because immunoglobulin therapy may reduce airways inflammation and improve the mucous expectoration(20). In our cases of immunodeficiencies and bronchiectasis, we have identified three definite primary immunodeficiencies (CVIDs & CGD) with early onset disease and six cases with variable causes of antibody deficiencies presented as an adult-onset disease.
The current ERS guidelines only recommend measurement of complete blood count along with IgG, IgA and IgM as the baseline set of investigation for immunodeficiency in bronchiectasis(1). Of course, with nonspecific signs/symptoms of immunodeficiencies, the more extensive investigations are likely to yield greater number of patients with a diagnosis albeit a much higher health-economic burden. In a recent study comparing five different sets of immunological investigations, Aliberti et al. were able to demonstrate that addition of IgG subtypes and lymphocyte subsets to the base investigations recommended in ERS guidelines resulted in a very significant increase in immunodeficiency diagnoses (8.9% vs 44.6% p < 0.001) and further addition of HIV test and IgE did not increase the diagnostic yield any further(10). IgG subsets were tested for in about 24% of patients in our cohort while none oh the patients had lymphocyte subsets tested which may partly account for lower immunodeficiency diagnosis in this study.
One obvious limitation of our study is the retrospective design which of course reduces the quality of the data and makes it difficult to exclude confounders. However, to date all the studies looking at the bronchiectasis etiology have been of retrospective observational nature and that could at least partly explain the heterogeneity of results. The lack of standardization of investigations especially the ones focused on immunodeficiency testing has also been a significant problem and probably leads to underestimation of this immunodeficiency disorders. The recent data form Aliberti et al. is likely to address this issue in near future(10).
In conclusion our study is the first one from the Middle Eastern region that shows aetiological factors in the regional population of Arab ethnicity. The data shows similarities to other western cohorts with high number of post-infective and idiopathic cases with high rate of pseudomonas colonization but contrasts in terms of higher post-TB and PCD related cases.