European Journal of Cardiovascular Medicine

Mycobacterium tuberculosis (MTB), identified by Robert Koch in 1882, is the foremost cause of mortality among adults. [1]Data is current until October 2023. In 2006, the World Health Organisation (WHO) estimated 9.2 million new cases of tuberculosis (TB), equating to 139 per 100,000 population. This figure included 4.1 million new smear-positive cases, representing 44% of the total, and 0.7 million HIV-positive cases, accounting for 8% of the total globally. This represents an increase from 9.1 million cases in 2005, attributable to population growth. [2] India, China, Indonesia, South Africa, and Nigeria occupy the first to fifth positions, respectively, in terms of absolute case numbers.The African region exhibits the highest incidence rate, at 363 per 100,000 population. [2]

Despite a significant number of pulmonary tuberculosis patients exhibiting negative AFB sputum results or lacking expectoration, the transmission rate of smear-negative TB is reported to be 22% in comparison to smear-positive TB.[3] Approximately 50% of pulmonary tuberculosis cases are Sputum smear negative for acid-fast bacilli.4 Published studies indicate that over 50% of smearnegative patients require chemotherapy if not addressed.[5-6] Administration of empiric Anti-Tuberculous Therapy (ATT) is indicated for patients exhibiting X-ray findings that strongly suggest pulmonary tuberculosis (PTB). Nonetheless, recurrent sputum smears negative for acid-fast bacilli (AFB) possess numerous drawbacks, including therapeutic failure in instances of multidrug-resistant tuberculosis (MDR-TB), adverse medication effects, and postponement in the diagnosis and treatment of non-tuberculosis conditions when they coexist.[7] Consequently, specimens other than sputum are crucial for patients with occult tuberculosis or similar conditions.Fiberoptic bronchoscopy (FOB) has been employed to acquire diverse samples for the diagnosis of sputum smear-negative pulmonary tuberculosis. The findings of these studies are contradictory and ambiguous. [8 -10 ]The overall efficacy of bronchoscopy for diagnosing tuberculosis has been documented. exceeding 90% when cultures were incorporated into the analysis, which is reported to be comparable even in sputum smear.negative tuberculosis.[11,12] Numerous studies have evaluated the efficacy of various samples for achieving an early diagnosis. This study was conducted at a tertiary care hospital to assess the importance of bronchoalveolar lavage specimen culture and acid-fast staining in comparison to sputum culture and staining for the diagnosis of pulmonary tuberculosis.

Study Design 

This study is a prospective analysis conducted over 18 months, from September 2022 to February 2024, to evaluate the diagnostic utility of bronchoalveolar lavage (BAL) in sputum smear-negative pulmonary tuberculosis (PTB). 

Study Setting 

The study was conducted at a tertiary care hospital, involving patients suspected of having PTB based on clinical history, physical findings, and chest X-ray lesions. 

Study Population 

Patients suspected of PTB who tested negative for acid-fast bacilli (AFB) on two sputum smear samples, as per Revised National Tuberculosis Control Program (RNTCP) guidelines, were included. 

Inclusion Criteria 

1. Patients with clinical history, physical findings, and chest X-ray lesions suggestive of PTB.
2. Sputum smear-negative patients for AFB on two separate samples.

Exclusion Criteria 

1. Patients with AFB smear-positive results.
2. Cases of extrapulmonary tuberculosis.
3. Patients on anti-tubercular treatment for suspected PTB based on clinical or radiological findings.
4. Patients with contraindications to bronchoscopy, such as significant hypoxemia (SpO₂ <90% at rest) or bleeding diathesis.

Sampling Technique and Size 

A complete enumeration approach was employed, analyzing all patients undergoing bronchoscopy within the defined 18-month period. 

Data Collection 

BAL samples were obtained from each patient during bronchoscopy. These samples were analyzed as follows: 

1. Smear Microscopy: For the detection of AFB.
2. Culture: For Mycobacterium tuberculosis.
3. Cartridge-Based Nucleic Acid Amplification Test (CBNAAT): To detect Mycobacterium tuberculosis DNA and determine rifampicin resistance.

All findings were recorded on pre-structured proformas designed for the study. 

Statistical Analysis 

Data were entered and processed using Microsoft Excel 2010. Descriptive statistics were used for quantitative variables, such as means and standard deviations (SD), and for categorical variables, such as frequencies and percentages. Pie charts and bar diagrams were used to visualize qualitative variables.  For inferential analysis, the chi-square test was applied to assess associations between qualitative variables. A p-value <0.05 was considered statistically significant, while a p-value >0.05 was deemed statistically insignificant.

Table 1: Age and Sex Distribution of Study Population

The study population consisted of 200 patients, with an age distribution spanning 11 to 70 years. The largest age group was 21–30 years, comprising 86 patients (43.0%), with 63 males (42.0%) and 23 females (43.4%). This was followed by the 31–40 age group, with 54 patients (27.0%), including 43 males (28.7%) and 11 females (22.2%). The 51–60 age group accounted for 13.0% of the population (26 cases), with 23 males (15.3%) and 3 females (6.0%), while the 61–70 group comprised 17 patients (8.5%), with 14 males (9.3%) and 3 females (6.0%). The 41–50 group included 11 patients (5.5%), all males (7.3%). The smallest group was 11–20 years, representing 6 patients (3.0%), all females. Overall, males made up 154 cases (75.7%), while females accounted for 46 cases (24.3%), indicating a predominance of male patients across most age brackets.

Table 2: Presenting Symptoms in the Study Population

The study population of 200 patients exhibited a range of presenting symptoms, with the most common being cough/expectoration, reported by 177 patients (88.6%). Fever was the second most frequent symptom, present in 171 patients (85.7%). Haemoptysis occurred in 77 cases (38.6%), while chest pain was noted in 34 patients (17.1%). Shortness of breath affected 23 patients (11.4%), and heaviness of chest was the least common symptom, seen in 6 patients (2.9%). This highlights the predominance of respiratory-related symptoms among the study population.

Table 3: Frequency of Chest Radiological Pattern in Study Population

Among the 200 patients in the study population, chest radiological patterns revealed that pulmonary infiltrates were the most common finding, observed in 111 cases (55.7%). Cavitary lesions were present in 60 patients (30.0%), while nodular shadows were noted in 17 cases (8.6%). Miliary mottling was the least frequent pattern, detected in 11 patients (5.7%). These findings highlight the diversity of radiological presentations in the study population.

Table 4: Distribution of Zonal Involvement in Study Population

The distribution of zonal involvement on chest X-rays among the 200 patients revealed that the right upper zone was the most commonly affected, observed in 120 cases (60.0%). The left upper zone showed involvement in 23 cases (11.4%), followed by the right mid zone in 17 cases (8.6%). The left mid zone was rarely affected, with only 3 cases (1.4%). Lower lung fields were involved in 9 cases (4.3%), while diffuse parenchymal involvement was seen in 28 cases (14.3%). These findings underscore the predominance of upper zone and diffuse parenchymal involvement in this study population.

Table- 5 Distribution of Bronchoscopic Diagnostic Findings

The table summarizes diagnostic findings from bronchoscopic procedures performed on 200 patients suspected of tuberculosis or alternate diagnoses. Among the tests, CBNAAT (Cartridge-Based NAAT) showed the highest positivity rate at 30% (60 cases), followed by AFB Culture with 25% (50 cases), and Z-N Stain & Cytology at 20% (40 cases). Aerobic Culture & Gram Stain had a positivity rate of 15% (30 cases), while 10% (20 cases) of the patients had no diagnostic findings. These results highlight the varying sensitivity of diagnostic tools in detecting tuberculosis and related conditions.

In our study, male patients outnumbered female patients. Gender bias in tuberculosis is widely questioned due to the lack of concrete evidence in global studies. However, a study from Brazil and the majority of authors indicate a higher incidence of sputum-positive pulmonary tuberculosis among males [13,14]. These data corroborate our study findings in sputum smear-negative cases. In developed countries, tuberculosis is more prevalent among the elderly, whereas in developing countries, it predominantly affects young and middle-aged individuals. Recent observations indicate a significant trend towards increasing age compared to two decades ago [15]. In Scotland in 1993, 64% of Caucasian tuberculosis patients were over 55 years old, whereas 85% of Asian patients were under 55 years old [16]. A study conducted in Pakistan, involving 5,023 cases of pulmonary tuberculosis, demonstrated that the disease predominantly affects the economically productive demographic, specifically individuals aged 15 to 59 years.[17] The current study revealed a markedly higher prevalence in the rural population, aligning with the National Family Health Survey findings, which documented a prevalence of 469 versus 307 per 100,000 population in rural areas.[18] Raine et al. identified poverty and illiteracy as significant contributors to tuberculosis in rural populations [19]. The clinical manifestations of pulmonary tuberculosis have exhibited notable consistency across decades, continents, and clinical environments; cough is observed in 70-90% of cases, weight loss in 43-75%, haemoptysis in 21-29%, and fever in 75-80% [20-24]. Fever is the most prevalent systemic effect symptom [25,26]. Cough is the most prevalent symptom associated with lung infection. [27,28][In our study, pulmonary infiltrate was the predominant radiographic finding, observed in 55.7% of patients. In cases of cavities accompanied by infiltrates, 85.7% of patients exhibited these characteristics. Aktogu et al. reported that pulmonary infiltrate was the predominant radiographic finding in 99% of patients in their study [20]. Cavities, when observed, are regarded as the most significant X-ray finding indicating active disease in adults. The incidence of cavities in chest X-rays among adults ranges from 40% to 87% [20, 28, 29]. Our study indicated that the miliary pattern constituted 5.7% of the total cases. While military tuberculosis is predominantly observed in the primary form of the disease, it can also manifest in 7% of post-primary cases. [30]The nodular form represents one of the rarer manifestations. Nyman et al. reported 7% in their study, Khan et al. reported 9%, whereas our study observed a nodular pattern in 8.6% of cases [31,32]. In two extensive studies comprising 204 and 500 patients, the locations of cavitary disease were identified in 83-85% of cases within the apical and/or posterior segments of the upper lobes, and in 11-14% of cases within the superior segments of the lower lobes [33, 34].  Parenchymal involvement is observed in multiple segments in the majority of cases [35, 36]. Our study reveals that there is an insignificant difference in clinical presentation and radiographic findings when comparing smear-positive and smear-negative cases. Confirmation of tuberculosis can solely be achieved through an AFB-positive sputum smear or a culture positive for Mycobacterium tuberculosis. Sputum smear-negative patients present a dilemma for physicians regarding the initiation of antitubercular therapy (ATD). Moreover, it is significant that 74% of these patients may progress to active tuberculosis within the subsequent five years if not adequately treated [37]. Bronchoscopy and associated procedures such as bronchoalveolar lavage (BAL), bronchial aspirate, bronchial brushing, transbronchial biopsy, and post-bronchoscopy sputum analysis may serve as alternative methods for achieving an early diagnosis. Bronchoalveolar lavage (BAL) is regarded as the most effective bronchoscopic specimen for diagnosing pulmonary tuberculosis [38]. Caminero et al. asserted that bronchoscopy ought to be conducted in all patients with negative sputum smears and concluded that bronchoalveolar lavage (BAL) should be a standard procedure due to its simplicity and relative safety [39]. The diagnostic yield of the bronchoscopic procedure in our study was 25.7%. The BAL smear was positive for AFB in 17.1%, and the mycobacterial culture was positive in 25.7%. S. Charoenratanakul et al. reported a diagnostic yield of positive BAL smear in 7.5% of cases and culture positivity in 155 cases [40]. Additional studies have identified elevated detection rates. Vijayan et al. discovered that BAL fluid culture yielded positive results in 34% of cases [41]. Comparable results have been documented by Kennedy et al [42]. Baughman et al. examined 50 patients and determined that the sensitivity of positive smear and positive culture in bronchoalveolar lavage (BAL) was 68% and 92%, respectively [43]. Purohit et al. conducted fibreoptic bronchoscopy on 50 patients, revealing that bronchoalveolar lavage (BAL) was positive for acid-fast bacilli (AFB) smear in 42% of cases, while BAL culture was positive in 70% of patients [44]. Some studies indicate that bronchoscopic specimens yield lower results, while others demonstrate significant findings, underscoring the importance of BAL fluid in diagnosing sputum smear-negative pulmonary tuberculosis. Sputum smear-negative pulmonary tuberculosis is a paucibacillary condition, and the dilution of epithelial lining fluid by instilled saline may account for the low yield from bronchoalveolar lavage specimens in certain studies. Furthermore, the local anaesthetic employed during bronchoscopy may have inhibited the proliferation of M. tuberculosis [45].

The findings from the bronchoscopic diagnostic tests in our study indicate that CBNAAT (Cartridge-Based NAAT) had the highest positivity rate at 30%, followed by AFB Culture at 25%, Z-N Stain & Cytology at 20%, and Aerobic Culture & Gram Stain at 15%. This distribution aligns with other studies that have reported varying diagnostic yields of bronchoscopy in tuberculosis cases. For instance, a study by Kanda et al. found that bronchoscopy yielded a diagnosis of pulmonary tuberculosis in 44% of patients, emphasizing its effectiveness, particularly when sputum samples are inadequate or negative [46]. Furthermore, a retrospective analysis indicated that bronchoscopy could achieve microbiological confirmation in nearly 49.1% of patients who were initially microbiologically negative for TB, showcasing its utility in complex cases [47]. In contrast, our study's finding of 10% of patients having no diagnostic findings highlights the limitations inherent in bronchoscopic procedures and the variability in diagnostic yield across different populations and methodologies [48]. Overall, while our results demonstrate the effectiveness of various bronchoscopic techniques, they also reflect the need for continued exploration of complementary diagnostic strategies to enhance detection rates for tuberculosis and related conditions.

Pulmonary tuberculosis remains a significant public health challenge, particularly in developing countries and among HIV-infected individuals worldwide. Diagnosing sputum smear-negative cases is critical for effective control and treatment. Fibreoptic bronchoscopy-guided bronchoalveolar lavage (BAL) is a safe and effective method for diagnosing such cases. Combining BAL fluid analysis with transbronchial lung biopsy and routinely culturing post-bronchoscopy sputum for Mycobacterium tuberculosis can enhance diagnostic yield.

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