Prevalence of Cystic Fibrosis and Pattern of Lung Function Impairment in Adults Presenting With Bronchiectasis at a Tertiary Care Hospital in Resource Poor Country Bangladesh: A Cross‐Sectional Study

ABSTRACT

Background and Aims

Bronchiectasis is a common but neglected respiratory condition, particularly in resource‐poor countries such as Bangladesh. Cystic fibrosis (CF), a recognized cause of bronchiectasis in children, especially among Caucasians, is increasingly reported in adults of Asian descent. However, CF remains under‐recognized in Bangladesh, and no prior data exist on its prevalence in adults. This study aimed to determine the prevalence of CF in adult bronchiectasis patients and to assess their lung function characteristics using spirometry in Bangladesh.

Methods

This cross‐sectional study was conducted in the Department of Respiratory Medicine at Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka, from June 2023 to November 2024. A total of 130 adults with bronchiectasis were enrolled in accordance with the inclusion and exclusion criteria. CF diagnosis was established using pilocarpine iontophoresis sweat chloride testing, and lung function severity was assessed by spirometry. Statistical analyses were performed using SPSS version 25.

Results

Among 130 participants, 12 were diagnosed with CF, representing 9.2% of patients. Obstructive airway abnormality was the predominant pattern among CF patients (75.0%), with half presenting in the mild category. A moderate negative correlation was observed between forced expiratory volume in 1 s (FEV₁ % predicted) and sweat chloride concentration (Cl⁻) (Spearman's rho = *−0.477, p = 0.117).

Conclusion

Approximately one in ten adult bronchiectasis patients in Bangladesh were found to have CF, and most had mild airway obstruction. These findings highlight that CF, traditionally regarded as a childhood disease, should also be considered in adult bronchiectasis, particularly in South Asian populations where it remains underdiagnosed.

Summary

• Adult bronchiectasis patients were evaluated for CF using the sweat chloride test and spirometry.

• CF was identified in approximately in 10% of cases, with mild airway obstructive disease common for this group. A non‐significant inverse correlation of lung function impairment with sweat chloride level was found, which needs further investigation with a larger cohort.

• Therefore, CF testing should be considered in etiological evaluation when dealing with adult bronchiectasis in the South Asian population.

1. Introduction

Bronchiectasis is a chronic respiratory disease characterized by a permanent abnormal widening of the proximal sub‐segmental bronchi, usually presenting with cough, daily sputum production, and recurrent lower respiratory infections with varying degrees of airflow limitation [1]. Although idiopathic in most cases, a wide range of identifiable inherited and acquired disorders are found as a causal factor [2].

The reported prevalence of bronchiectasis in Europe and North America is 67 to 566.1 per 100,000 [3]. The true prevalence of bronchiectasis in Asia is unknown because of limited research. Data from the Indian bronchiectasis registry shows that the most common cause is idiopathic, despite the higher incidence of post‐TB bronchiectasis [4].

Cystic fibrosis is one of the underlying causes of bronchiectasis. It is the most common manifestation of the autosomal recessive multisystem disorder caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. This causes airway dehydration, resulting in bacterial infection and inflammation. The presence of severe mutations in both alleles of the CFTR gene typically leads to classical cystic fibrosis with multisystem involvement presenting in early childhood. In contrast, different milder mutations in each allele may allow partial CFTR function. This may lead to milder, single‐system involvement such as isolated bronchiectasis, which can present in adulthood [5].

Since both CF and bronchiectasis share common clinical features, it may be reasonable to consider CFTR dysfunction as the etiological agent in idiopathic bronchiectasis [6]. In a study conducted by Casals et al. in Barcelona, Spain, CFTR mutations were identified in 36% of 55 adult patients with idiopathic bronchiectasis [7]. A 10‐year retrospective study in Paris involving 601 adults with diffuse bronchiectasis (mean age 31 years; range 18–56 years) identified CF in 46 patients (7.6%) [8]. However, the true prevalence of adult CF in Bangladesh remains unknown due to a lack of data.

Due to limited access to diagnostic facilities in Bangladesh, the exact cause of adult bronchiectasis apart from post‐infection is often not assessed, and most cases are labeled as idiopathic. Early identification of CF is important to help guide treatment to slow disease progression. CF is diagnosed on the basis of clinical features and the presence of evidence of CFTR dysfunction. CFTR dysfunction can be identified by the sweat chloride test. This test measures sweat chloride concentration (Cl⁻) following pilocarpine iontophoresis stimulation. It remains the gold standard initial test for diagnosing CF and is recommended by the United States Cystic Fibrosis Foundation [9].

Lung function is an important predictor of survival in patients with CF. Chronic infection and inflammation contribute to airway remodeling and the development of bronchiectasis, leading to progressive lung function decline. Studies suggest that lung function is better preserved in individuals with late‐onset CF compared to those with childhood‐onset disease [10]. Ethnicity has been shown to impact lung function among CF patients, with studies demonstrating that Asian CF populations have lower baseline lung function compared to their non‐Asian counterparts [11, 12].

Our study aimed to determine the prevalence of cystic fibrosis among adult patients with bronchiectasis attending a tertiary care center in Bangladesh, describe the patterns of lung function impairment, and assess the relationship, if any, between lung function severity and sweat chloride concentration (Cl⁻).

2. Materials and Methods

This cross‐sectional observational study was conducted in the Department of Respiratory Medicine of Bangabandhu Sheikh Mujib Medical University (BSMMU) in Dhaka, Bangladesh, after taking ethical approval from the Institutional Review Board (IRB), from June 2023 to November 2024. BSMMU is the tertiary referral teaching hospital with 4000 resident doctors and 500 faculty members, working in 56 departments. The study enrolled a total of 130 adult patients of both sexes diagnosed with bronchiectasis with chronic respiratory symptoms and high‐resolution computed tomography (HRCT) of the chest confirmed bronchiectasis. Exclusion criteria were traction bronchiectasis associated with interstitial lung disease, patients with known post‐ tuberculosis bronchiectasis, patients who were unable or unwilling to provide informed consent, pregnant patients, and patients with known hypothyroidism, hypoparathyroidism, hypoadrenalism, eczema, and skin infection. Non‐probable consecutive sampling was employed. The sample size for our study was calculated using a formula

$$n=\frac{{[u\sqrt{\pi (1-\pi )}+v\sqrt{{\pi }_0(1-{\pi }_0)}]}^2}{{(\pi -{\pi }_0)}^2},$$

where n = estimated sample size; u = 1.96 (in 95% confidence interval) value of standard normal distribution; V = 0.84 (80% power); π = 7.6% or 0.076 prevalence of cystic fibrosis in adult bronchiectasis [8]; π ₀ = 2% or 0.02 (expected frequency). Based on the calculation, a sample size was 129.5 and considering feasibility and anticipating potential participant dropout, we increased the sample size to 130.

The patients were given an explanation of the purpose, procedure, potential physical and psychosocial risks, and right to refuse to participate in this study. After taking written informed consent, detailed history‐taking and clinical examination were performed. Participants then underwent sweat testing and spirometry.

Sweat test was conducted using pilocarpine iontophoresis to measure the sweat chloride concentration (Cl⁻) in patients. The procedure was performed in two steps. First, sweat was stimulated by applying pilocarpine iontophoresis. A 0.5% pilocarpine nitrate‐soaked disc was placed on the patients' forearm, and an electrode probe was used to deliver a current of 1.5 mA for 5 min. This process induced sweating in the area. After sweat stimulation, the chloride concentration (Cl⁻) was directly measured using a detachable skin electrode. The electrode was placed in the same area where the pilocarpine was applied, and the measurement was taken over an additional 10‐min period using the SM‐01 sweat analyzer manufactured by SANASOL–Hungary, which determines the chloride concentration (Cl⁻) in sweat based on chloride equivalent levels. Sweat chloride concentration (Cl⁻) levels were categorized as follows: normal (< 30 mmol/L), intermediate (30–59 mmol/L), and positive for cystic fibrosis (CF) (≥ 60 mmol/L). Definitive diagnostic criteria for CF in non‐screened populations were set using the following criteria: presence of CF symptoms or a family history and sweat chloride concentration ≥ 60 mmol/L [9].

Pulmonary function was done by spirometry using a Micro Quark PC‐based spirometer, manufactured by COSMED–Italy, and results were categorized as normal, obstructive, restrictive, and mixed airway disorders. Key parameters, forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1), were measured and expressed as percentages of the predicted values. The Global Lung Function Initiative (GLI) race neutral equation was used for calculating the percentage of predicted value, and FEV1/FVC ratio was calculated in accordance with the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guideline, where cutoff value of < 0.7 was fixed for obstructive airway defect [13]. Lung function is categorized as (a) normal = FEV1/FVC ratio ≥ 70, and both FEV1 and FVC % predicted > 80%, (b) obstructive = FEV1/FVC ratio < 70% and FEV1% predicted < 80%, (c) restrictive = FEV1/FVC ratio ≥ 70% and FVC% predicted value < 80%, (d) mixed = FEV1/FVC ratio < 70% and both FEV1 and FVC % predicted < 80%. Severity of obstructive defect was assessed by FEV1% predicted and classified in accordance with ATS/ERS recommendation as (a) mild (> 70%), (b) moderate (60%–69%), (c) moderately severe (50%–59%), (d) severe (35%–49%), and (e) very severe—< 35%. Due to a lack of total lung capacity, the severity of the restrictive defect assessed by FVC % predicted as (a) mild (< 70%–80%), (b) moderate (60%–69%), (c) moderately severe (50%–59%), (d) severe (35%–49%), and (e) very severe < 35%) [14, 15].

SPSS version 25 was used for data analysis. Categorical variables were presented as proportions and percentages, while continuous variables were checked for normality by Shapiro–Wilk test and expressed as median, and interquartile range (IQR). The Kruskal–Wallis test was used to compare lung function results across normal, intermediate sweat chloride level groups. The severity of spirometric impairment was compared between patients with and without cystic fibrosis (CF) using the Fisher's exact test. Spearman's test was used to assess the correlation between FEV1% predicted and sweat chloride concentration (Cl⁻) within the CF group. A p value of less than 0.05 was considered statistically significant, with a 95% confidence interval.

3. Results

A total of 130 known bronchiectasis patients aged 18 years or older were included in this study. Out of them, 12 patients were identified as CF based on the sweat chloride test, representing 9.2% of the sample, followed by 19.3% of cases had intermediate‐range sweat chloride values (Figure 1). In CF patients, the mean sweat chloride concentration was 66.9 mmol/L (range 60–87 mmol/L), with a median of 65.0 mmol/L.

Figure 1.

Distribution of the studied participants by pilocarpine sweat chloride test results (N = 130). Pie diagram showing the distribution of the study participants by pilocarpine sweat chloride test results (N = 130). It shows that 9.2% of participants had sweat chloride value above the cut‐off value (≥ 60 mmol/L), whereas 19.3% of participants had within the intermediate range (30–59 mmol/L), and rest 71.5% of participants had a normal sweat test value (< 30 mmol/L).

Lung function assessed by spirometry revealed that 75.0% of adult CF patients had isolated obstructive airway defects, while 25.0% had mixed airway defects, with no cases of isolated restrictive defects. In contrast, among non‐CF patients, the predominant abnormality was restrictive airway defects (31.4%), followed by obstructive airway defects (29.7%) and mixed airway defects (19.5%). Lung function remained within normal range in 19.5% non‐CF patients, whereas all CF patients exhibited abnormal lung function (p = 0.002) (Figure 2).

Figure 2.

Patterns of lung function abnormality in the studied participants (N = 130). *p value was 0.002, calculated using Fisher–Freeman–Halton Exact Test. p value < 0.05 was considered as a level of significance. Pattern of lung function abnormality in the study participants (N = 130). Isolated obstructive defect (75.0%) was the most common lung function abnormality, followed by mixed defect (25.0%) in CF patients. No isolated restrictive defect was identified in CF patients. Among non‐CF patients, the predominant lung function abnormality was restrictive defects (31.4%), followed by obstructive defects (29.7%) and mixed airway defects (19.5%). Lung function remained within normal range in the remaining 19.5% non‐CF patients.

When patients were subdivided by severity of obstructive airway defect, mild obstruction (FEV₁> 70% predicted) was significantly more prevalent in the CF group than in the non‐CF group (50.0% vs. 8.6%, p= 0.002). Severe and very severe obstruction were more common in the non‐CF group (31.0% and 32.8%) than the CF group (0.0% and 16.7%) but these differences did not reach statistical significance (p > 0.05) (Table 1).

Table 1.

Severity of airflow obstruction (FEV1% predicted) in CF and non‐CF patients with obstructive ventilatory defect (N = 130).

Severity of obstructive defect (FEV1% predicted)c	CF (sweat Cl− ≥ 60 mmol/L)a		Non‐CF (sweat Cl− < 60 mmol/L)b		p value*
	n	%	n	%
Mild (> 70% predicted)	6	50.0%	5	8.6%	0.002
Moderate—(60–69)% predicted	1	8.3%	9	15.5%	0.846
Moderately severe—(50–59)% predicted	3	25.0%	7	12.1%	0.476
Severe—(35–49)% predicted	0	0.0%	18	31.0%	0.061
Very severe—< 35% predicted	2	16.7%	19	32.8%	0.446
Total	12	100.0%	58	100.0%

Note: All 12 CF‐patients and 58 non‐CF patients had obstructive ventilatory defects. Among CF patients, obstruction was mild in 50% and moderately severe in 25%. Among non‐CF patients, most (32.8%) had very severe obstruction, followed by 31.0% had severe obstruction. The difference in severity between CF and non‐CF patients was statistically significant only in mild obstructive defect (p value = 0.002).

^a CF = cystic fibrosis.

^b Non‐CF = non cystic fibrosis.

^c FEV1% predicted = forced expiratory volume in the first second, expressed as a percentage of predicted.

^* p value obtained by Fisher's exact test, p value < 0.05 was considered as a level of significance.

Among the CF patients with restrictive defect, there was one CF patient in each of the mild, moderate, and severe categories, respectively (33.33% in each) as part of a mixed defect. Among non‐CF patients, 20 (33.3%) had moderately severe, 17 patients (28.3%) had mild, 10 patients (16.7%) had moderate, 10 patients (16.7%) had severe, and 3 (5.0%) had very severe restrictive defect. The difference was not statistically significant among the two groups (p > 0.05 in all severity categories) (Table 2).

Table 2.

Severity of airflow restriction (FVC% predicted) in CF and non‐CF patients with restrictive ventilatory defect (N = 130).

Severity of restrictive defect (FVC % predicted)c	CF (Sweat Cl− ≥ 60 mmol/L)a		Non‐CF (Sweat Cl− < 60 mmol/L)b		p value*
	N	%	n	%
Mild—(< 80–70)% predicted	1	33.3%	17	28.3%	1.00
Moderate—(60–69)% predicted	1	33.3%	10	16.7%	1.00
Moderately severe—(50–59)% predicted	0	0.0%	20	33.3%	0.56
Severe—(35–49)% predicted	1	33.3%	10	16.7%	1.00
Very severe—< 35% predicted	0	0.0%	3	5.0%	1.00
Total	3	100.0%	60	100.0%

Note: Three CF‐patients and sixty non‐CF patients had restrictive ventilatory defect. There was only one CF‐patient each in the mild, moderate, and severe categories (33.33% each), respectively as part of a mixed defect. While among non‐CF patients, the majority had moderately severe, followed by mild and moderate restrictive defects, and the difference was not statistically significant in between groups.

^a CF = cystic fibrosis.

^b Non‐CF = Non cystic fibrosis.

^c FVC % predicted = forced vital capacity expressed as a percentage of predicted.

^* p value obtained by Fisher's exact test, p value < 0.05 was considered as a level of significance.

There were no statistically significant differences in median value of FEV₁ % predicted or FVC % predicted across different sweat chloride categories (p = 0.29 and p = 0.45, respectively). However, the FEV₁/FVC ratio was deferred significantly (p = 0.008), with the lowest median in the CF range (61.1), followed by intermediate range (67.7) and normal range (76.3) of sweat chloride category (Table 3). There was a moderate negative correlation between median FEV1% predicted and sweat chloride concentration (Cl⁻), but this was not statistically significant (rho = −0.477, p = 0.117) (Figure 3).

Table 3.

Lung function parameters by spirometry within different sweat chloride groups (N = 130).

Lung function indicesa	Sweat chloride groups			p value*
	Normal range (< 30 mmol/L) (n = 93)	Intermediate range (30–59 mmol/L) (n = 25)	CF range (≥ 60 mmol/L) (n = 12)
FEV1% predictedb	60.0 (37.5–85.0)	51.0 (36.0–78.5)	67.5 (51.87–77.0)	0.29
FVC % predictedc	76.0 (58.0–85.0)	76.0 (51.50–85.0)	81.6 (78.01–85.6)	0.45
FEV1/FVC ratiod	76.3 (60.7–92.0)	67.7 (60.05–86.7)	61.1 (58.4–65.2)	0.008

Note: The median (IQR) value of FEV1/FVC ratio was 61.1 (58.4–65.2) in the CF group, which was the lowest among different sweat chloride concentration groups (p value: 0.008). The median (IQR) value of FEV1% predicted was 67.5 (51.87–77.0) in the CF group. FEV1 and FVC % predicted value didn't show a significant difference across different sweat chloride concentration groups.

^aLung function indices were presented as median and interquartile range values.

^b FEV1% predicted = forced expiratory volume in the first second, expressed as a percentage of predicted.

^c FVC % predicted = forced vital capacity expressed as a percentage of predicted.

^d FEV1/FVC ratio = ratio of FEV1 and FVC % predicted.

^* p value was calculated using the Kruskal–Wallis analysis test. p value < 0.05 was considered as a level of significance.

Figure 3.

Correlation of median FEV1% predicted with sweat chloride concentration among CF patients (N = 12). rho = −0.477, p = 0.117. Scatterplot showing the relationship between FEV1 % predicted and sweat chloride concentration among patients in the CF range (N = 12). FEV1 % predicted showed moderate negative correlation with sweat chloride concentration among CF patients (rho = −0.477, p = 0.117).

4. Discussion

Bronchiectasis is a chronic, debilitating lung condition with a wide spectrum of underlying etiology. Although the condition is prevalent in Bangladesh, the underlying etiology remains undiagnosed in most cases due to limited awareness and testing facilities. However, identification of the underlying cause is crucial, as appropriate treatment of the cause can reduce disease progression and improve prognosis. Cystic fibrosis is an important underlying cause of bronchiectasis resulting from a mutation in the CFTR gene that maintains airway hydration. In its most recognized form, the severe CF, presents in the early years of life. It is now known that a less severe form of disease, single organ involvement, is the presentation in later adult life. This has led to the recognition of CF as a cause of bronchiectasis in adults [8]. While cystic fibrosis is prevalent among Caucasians and is well‐documented in established registries, data on the prevalence of CF in Asia have primarily been derived from retrospective studies or case reports published in the past two decades [8]. These gaps prompted us to conduct this study to determine the prevalence of CF as an underlying cause in adult patients with bronchiectasis at a tertiary care hospital in Bangladesh, marking the first such study of its kind.

The diagnostic criteria for CF apply to both adults and children, as outlined by Farrell et al. [9]. If a non‐smoking patient presents with long‐standing sinopulmonary disease, clinicians should consider CF as a potential cause. Confirming the diagnosis requires evidence of CFTR dysfunction. The sweat chloride test through pilocarpine iontophoresis, which indicates CFTR activity, remains the most important diagnostic test for CF in adults and should be the first test in any suspected case.

A pilocarpine iontophoresis sweat chloride test was performed on 130 patients who met the inclusion and exclusion criteria. Twelve patients (9.2%) were diagnosed as CF as indicated by a sweat chloride concentration (Cl⁻) value ≥ 60 mmol/L, while 25 patients (19.3%) fell within the intermediate range (30–59 mmol/L). Our findings demonstrated a slightly higher proportion of adult CF patients compared to a study conducted in Paris [8], where 46 CF patients were identified out of 601 bronchiectasis patients, representing a prevalence of 7.6%. The observed difference might be attributed to the relatively small sample size in our study, which was conducted at a national referral center in Bangladesh. The mean sweat chloride concentration (Cl⁻) of CF patients in our study was 66.91 ± 8.08 mmol/L, which was comparable to other studies [16, 17], where adult CF patients had a lower mean of sweat chloride concentration (Cl⁻) (75 ± 26 mmol/L) than children. Our results also concurred with findings from Bosch et al. [12], who reported a lower mean sweat chloride concentration (Cl⁻) (92 ± 26) in the Asian CF patients.

A significant number of patients (19.2%) in our study fell within the intermediate sweat chloride range (30–59 mmol/L) but did not undergo additional CFTR physiological testing due to resource constraints. If further CFTR physiology testing had been conducted in these patients, additional cases of CF might possibly have been detected from patients. This suggests that CF is more prevalent among the adult population in Bangladesh than previously assumed, challenging the perception that CF is rare in the Asian population. Hence, the pilocarpine sweat chloride test should have been more widely implemented in this setting to screen this population.

In this study, the median age of CF was 43.0 years with IQR (29–55 years), and the male‐to‐female ratio was 3:1, indicating the influence of ethnic variability in CFTR mutations on clinical expression [12].

The majority of individuals with CF typically exhibit an obstructive pattern likely due to chronic small airway inflammation leading to structural damage, mucus accumulation, and obstruction, reflecting the underlying disease pathophysiology [5, 10]. However, as the disease progresses, a restrictive or mixed pattern may emerge, which is also evident in this study as mixed airway abnormalities affected 25% of CF patients. This may be due to sampling from outpatients and the emergency department, where patients were undergoing disease exacerbation, as increased mucous secretion associated with advanced disease may present a mixed pattern of spirometry abnormalities.

Regarding the severity of lung function, CF patients in this study had a significantly higher rate of mild airway obstruction (p value: 0.002), while non‐CF patients had more severe and very severe obstruction, though the differences were not statistically significant. This can be explained by the fact that adults with CF often have residual CFTR activity, which leads to a less severe and less progressive disease [5, 10]. By comparison, chronic childhood lung diseases or untreated recurrent lung infections may be the reason behind non‐CF bronchiectasis in Bangladesh, and tendency to visit healthcare center in advanced disease stage as well can cause the observation of severe lung damage and severe airflow obstruction by the time it is diagnosed.

According to a review article by Meenu Singh et al. [11], Asian CF patients have lower mean FVC and FEV1 (58.5% and 76.8%, respectively), compared to Caucasians (79.8% and 100.3%, respectively). A retrospective observational study in 2021 in the United Arab Emirates (UAE) [18] also reported lower lung function in adult CF patients (median FEV1 49.5%, IQR 38.5–62.5). The US Cystic Fibrosis Foundation 2023 Patient Registry Annual Data Report [19] suggests a wide range of lung function issues, with median FEV1% predicted at 85.2% in cases of adults. Our findings align with the studies in Asia [11], showing obstruction as the most common airway abnormality in CF patients with a lower median FEV1% predicted at 67.5 (IQR: 51.87–77.0) compared to the US registry [19]. When comparing the median value of spirometry indices across different sweat chloride groups, though no significant differences were found for FEV₁ and FVC, the FEV₁/FVC ratio was significantly different (p value: 0.008) between groups, suggesting that FEV₁/FVC ratio may be a more sensitive measure of lung function change than absolute lung volumes.

Sweat chloride concentration is an indicator of CFTR activity and may correlate with the severity of lung function impairment. A 13‐year cohort study in 2015 by McKone et al. found that sweat chloride levels were significantly associated with longitudinal lung function decline (FEV1% predicted), when genotype is unknown [20]. Similarly, a 2017 retrospective study by Caudri et al. reported a consistent and significant negative correlation between sweat chloride concentration and FEV1% predicted [21]. Articles have also reported similar mechanisms in CF, where impaired ion transport results in mucus stagnation, inflammation, and subsequent lung function decline [5, 10]. Our study observed a non‐significant inverse negative linear correlation (rho = −0.477, p = 0.117) between sweat chloride concentration and FEV1% predicted. This finding indicates that increased sweat chloride concentration, a reflection of CFTR dysfunction, may be related to more severe airflow obstruction, but it does not establish a prognostic association in this cohort. The absence of statistical significance in this study may be attributed to the small sample size and should be further investigated with a larger cohort, as lung function deterioration can be reduced and even improved in some patients with recent advances in CF care, including CFTR modulator therapies [22, 23].

Our study had a few limitations. It was conducted at a single center with a small sample size, which may not accurately represent the broader population, and we were unable to perform genetic mutation analysis or other physiological tests due to the absence of such types of testing methods in this country, which may underscore our true CF prevalence, especially relevant for the intermediate sweat chloride group. Lack of genetic testing facilities is a major barrier in countries like Bangladesh, and this should be addressed by establishing a national CFTR mutation analysis center as well as a national CF registry, which may aid in precision diagnosis, determination of local mutation spectrum, and facilitation of future access to CF therapies. Sweat chloride testing facilities, despite being relatively low‐cost, are also of limited availability. Despite having these limitations, the results support the need for accurate diagnosis of CF in adults with bronchiectasis.

5. Conclusion

This study highlights the need to consider cystic fibrosis as a potential etiological factor in adult patients presenting with bronchiectasis. Obstructive airway defect was found to be predominant lung function abnormality in three‐quarters of CF patients with a mild severity in majority. Moreover, the observed non‐significant inverse relationship between sweat chloride concentration and FEV1% predicted should be explored in larger longitudinal cohorts to assess whether baseline sweat chloride level may serve as a prognostic marker of lung function decline.

Author Contributions

Shuvo Majumder: conceptualization, methodology, data curation, investigation, formal analysis, visualization, resources, writing – original draft, writing – review and editing, funding acquisition. Pujaneeta Biswas: conceptualization, methodology, data curation, investigation, writing – review and editing. Manal Mizanur Rahman: conceptualization, methodology, software, data curation, formal analysis, writing – review and editing. Md Sohidul Islam: investigation, writing – review and editing. Md. Mizanur Rahman: Investigation, writing – review and editing. Susanta Kumar Paul: resources, writing – review and editing. Md. Hamza: resources, writing – review and editing. Mohammed Humayun Kabir: resources, writing – review and editing. Samprity Islam: writing – review and editing. Fazle Rabbi Chowdhury: validation, writing – review and editing. Rajashish Chakrabortty: conceptualization, methodology, validation, project administration, writing – review and editing. Shamim Ahmed: conceptualization, methodology, validation, project administration, writing – review and editing. Mohammed Atiqur Rahman: conceptualization, methodology, validation, supervision, project administration, writing – review and editing.

Ethics Statement

This study was performed in accordance with the Declaration of Helsinki. This human study was approved by the Institutional Review Board (IRB), Bangabandhu Sheikh Mujib Medical University, Dhaka, Bangladesh– approval: 4456. All adult participants provided written informed consent to participate in this study.

Conflicts of Interest

The authors declare no conflicts of interest.

Transparency Statement

The lead author, Dr. Shuvo Majumder, affirms that this manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained.

Data Availability Statement

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.