Revista Americana de Medicina Respiratoria - Volumen 21, Número 3 - Septiembre 2021

Artículos Originales

Comparative study of the performance of GeneXpert MTB/RIF in bronchoalveolar lavage compared to bronchial lavage in patients with clinical suspicion of tuberculosis

Autor : Muñoz Luis1 *, Gallego Claudio1, Joza Karla1, Marchetti Eliana2, Cordoma Natalia2, Poropat Alejandra1, Armitano Rita Ines2, Salomone César1*

1Department of Respiratory Medicine, Hospital General de Agudos Parmenio P. Piñero CABA 2Central Laboratory, Bacteriology Section, Hospital General de Agudos Parmenio P. Piñero CABA

Correspondencia :Luis Muñoz. E-mail: luismcneumo@gmail.com

Abstract

Tuberculosis (TB) is one of the ten leading causes of death worldwide, and the main cause from a single infectious agent. Early detection of the Mycobacterium tuberculosis complex (MTC) and of mutations conferring resistance to the main drugs used in antituberculous treatment contributes to reducing the transmission of the infection, and consequently the spread of resistant TB. The GeneXpert MTB/ RIF test identifies the MTC and simultaneously detects mutations most frequently associated with rifampicin resistance, through real-time PCR testing.

The purpose of this study was to compare the performance of the GeneXpert MTB/RIF method in bronchoalveolar lavage (BAL) with bronchial lavage (LB) in immunocompetent patients with clinical suspicion of pulmonary TB without any previous microbiological documentation.

Materials and Methods: We prospectively enrolled patients with radiologic pulmonary infiltrates compatible with active or residual TB without previous treatment, with negative direct bacilloscopy or nonproductive cough, for the assessment of active disease. We identified the most affected segment through computed axial tomography and bronchoscopy with BAL in said segment, followed by BL of the affected lobe. A BAL recovery > 40% was considered significant. The samples obtained were processed for bacilloscopy, culture and GeneXpert MTB/RIF. We analyzed sensitivity (S), specificity (SP), positive predictive value (PPV) and negative predictive value (NPV), taking the solid culture medium as reference for the diagnosis of MTC.

Results: We included 20 patients; 3 were excluded because they didn’t have a representative BAL sample. 17 patients were evaluated (11 women, 65%), age 37.2 ± 16.3. The MTC was identified through conventional methods in 10 patients: 10 with positive culture in BL and 9 in BAL.

In comparison with the conventional methods, 6 out of 17 samples obtained through BAL had a positive result for GeneXpert MTB/ RIF: S = 60.0% (CI 31%-83%), SP = 100% (CI 65%-100%), PPV = 100% (CI 61%-100%) and NPV = 64% (CI 35.4%-84.8%). With BL, 9 out of 17 had a positive result for Xpert MTB/RIF: S = 90.0% (CI 60%-98%), SP = 100% (CI 65%-100%), PPV = 100% (CI 70%-100%) and NPV = 88% (CI 53%-98%). All the cases identified with GeneXpert MTB/RIF were true positives in relation to conventional cultures.

Conclusion: Considering the solid culture as reference method, the BL was more sensitive than the BAL for the diagnosis of tubercu­lous infection through the GeneXpert MTB/RIF method in patients with suspected TB without previous microbiological documentation.

Key words: Tuberculosis; Bronchoalveolar lavage; Comparative study

Received: 12/15/2020

Accepted: 06/29/2021

Introduction

Tuberculosis (TB), a preventable and curable condition, is one of the most widespread infectious dis­eases around the world and constitutes an important threat to public health. There are approximately 2 billion people around the world infected with the Mycobacterium tuberculosis complex (MTC). Every year almost 9 million people develop the active disease and 2 million people die from it1.

The microbiological diagnosis of TB is complicated. The bacilloscopy is a fast, simple, low-cost tech­nique but has low sensitivity2, 3. Although the culture test is still the reference method or gold standard for the diagnosis of all types of TB because it allows for gender and species identification, it requires higher level laboratories with more demanding infrastructure and equipment conditions, and the results are obtained after 15 days and even 8 weeks of incubation of the clinical samples.

Early detection of the MTC and of mutations conferring resistance to the main drugs used in anti­tuberculous treatment has a great impact on the management, prognosis and evolution of the disease apart from contributing to reduce the transmission of the infection, and consequently the spread of resistant TB1-4.

In this regard, during the last years different molecular biology techniques have emerged noticeably accelerating the TB diagnosis in comparison with the use of bacilloscopy and culture.

The GeneXpert MTB/RIF test is based on the detection of MTC-specific nucleic acids through real-time PCR testing. The GeneXpert MTB/RIF simultaneously identifies the MTC and detects the rpoB gene mutations more frequently associated with resistance to rifampicin, the most important drug against this disease. Itis a completely automated process that allows the diagnosis within a period of two hours2. The WHO (World Health Organization) recommends this test for the initial diagnosis of TB1-4.

In patients with clinical suspicion of TB and nonproductive cough or negative bacilloscopy, respiratory samples can be obtained for infectious analysis through bronchoscopy, providing an early diagnostic confirmation5-9.

The flexible bronchoscopy is a diagnostic and therapeutic procedure essential for respiratory medi­cine6,7. Bronchoalveolar lavage (BAL) is the reference bronchoscopic sample for the study of infectious diseases that affect the pulmonary parenchyma8, 9, and bronchial lavage (BL) is a complementary sample due to the possibility to be contaminated with secretions from the upper respiratory tract.

When the BAL is not available or the samples obtained are not significant for the analysis, the ques­tion arises as to consider the BL as the representative sample for the etiologic study in the situations previously mentioned.

The purpose of this study was to compare the performance of the GeneXpert MTB/RIF method in BAL with BL in immunocompetent patients with clinical suspicion of pulmonary TB, without previous microbiological documentation, in order to optimize the use of diagnostic resources.

Materials and Methods

This prospective, cross-sectional study was conducted at the Department of Respiratory Medicine and the Central Laboratory, Bacteriology Section of the Hospital General de Agudos Parmenio Piñero, within the period from June 2018 to December 2019.

All the bronchoscopy procedures were performed by the staff of the Respiratory Medicine Division. We used a videobronchoscope of the 70K series with a diameter of 6.2 mm (model EB - 1970K, PENTAX). All visible bronchi and pulmonary segments were examined through topical anesthesia; and samples were collected from the pulmonary segment or subsegment which showed abnormal lesions suggestive of active TB in the HRCT (High Resolution Computed Tomography).

For the BAL, 100 to 120 ml of saline solution 0.9% were instilled in five or six aliquots, the first being separated and attached to the BL. The BL was done after the BAL. 20-40 ml of saline solution 0.9% were instilled in the other pulmonary segments involved, and aspirated until 20 to 30 ml of liquid were collected in the suction trap: then the first aliquot obtained with the BAL was added.

We excluded patients in whom the BAL couldn’t be performed or those who didn’t have significant samples. A BAL recovery > 40% was considered significant. There weren’t any complications during the procedure.

Samples obtained were divided and referred for bacteriological and cytological studies. At the Bacte­riology Service each sample was divided in two: one part was used for identifying the MTC and detect­ing sensitivity to rifampicin by GeneXpert MTB/RIF, whereas the remaining aliquot was used for the bacilloscopy and culture in a liquid medium (MGIT 960, Becton Dickinson-BD) and in a solid medium (Löwenstein Jensen and Stone Brink).

We determined sensitivity (S), specificity (SP), positive predictive value (PPV) and negative predic­tive value (NPV) taking the culture in solid medium, Löwenstein-Jensen and Stone Brink as method of reference.

Results

3 of the 20 patients included in the study (15%) were excluded because they obtained an insufficient volume with the BAL (Figure 1).

Imagen
Figure 1. Flow of patients included in the analisys

17 patients were evaluated (11 women, 65%), with a mean age of 37.2 ±16.3 years. Distribution per nationality was: 10 (59%) Argentinians, 6 (35%) Bolivians and 1 (6%) Peruvian. Most patients didn’t show comorbidities (n = 15, 88%) and didn’t have a history of TB (n = 16, 95%). The most frequently found lesions were infiltrates or consolidations in the upper lobes (n = 17, 100%).

The combination of the results of the BAL and BL samples allowed us to identify 10 patients with MTC through conventional methods (one with positive bacilloscopy in BL, 10 with positive cultures in BL and 9 in BAL); the remaining cases were clinically followed-up.

6 out of the 17 samples obtained through BAL were positive with GeneXpert MTB/RIF: S = 60.0%, SP = 100%, PPV= 100% and NPV = 64%.

With BL, 9 out of 17 had a positive result for GeneXpert MTB/RIF: S = 90.0%, SP = 100%, PPV = 100% and NPV = 88%. All the cases identified with GeneXpert MTB/RIF were true positives in relation to conventional cultures. The results obtained are shown schematically and with confidence intervals in Table 1.

Table 1. Comparison of the Xpert MTB/RIF performance
Imagen

In this study we didn’t assess the importance of the GeneXpert MTB/RIF test in detecting resistance to rifampicin in FBC (fibrobronchoscopy) samples, though they weren’t detected in patients under evaluation.

Discussion

The bronchoscopic diagnosis of pulmonary tuberculosis is traditionally based on bacilloscopy and MTC culture. The genomic analysis through nucleic acid amplification techniques such as the GeneXpert MTB/RIF allows for a rapid, high-sensitivity diagnosis.

Given the fact that WHO recommendations on GeneXpert MTB/RIF only refer to sputum samples, more research is necessary on the use of this PCR in bronchoscopic samples.

Le Palud et al, 2014 conducted a retrospective, observational study about the diagnostic precision of the GeneXpert MTB/RIF test in fibrobronchoscopic samples, where the type of sample was left to the discretion of the specialist according to the patient’s tolerance to treatment10.

In our work, the diagnostic performance of the BL turned out to be superior to that of the BAL for the identification of active pulmonary TB. With regard to other studies that analyze the BAL11, 12 or the BL13, 14 performance individually, we compared the performance of GeneXpert MTB/RIF in BAL and BL together in the same procedure in patients with clinical suspicion of TB and we considered the culture as reference method. We observed that the BAL was less sensitive than the BL for the diagnosis of TB (60% versus 90%, respectively), with the same specificity (100%).

Bronchial lavage is referred to in research done in Japan (Kohno, Kurashima and Takano), India (Arshad, Gupta15) and South Korea (Yoo, Song) as the reference sample for the study of TB, using BAL for other respiratory diseases. Those are centers with high incidence of TB.

One limitation to the work is the small sample of individuals included. Another observation regarding the procedure used for sample collection (BL after BAL, including the same segment already assessed with the latter) is that we could infer a better diagnostic performance of the BL when we include the residual material from the BAL.

Conclusion

Considering the solid culture as reference method, the bronchial lavage was more sensitive than bron­choalveolar lavage for the diagnosis of tuberculous infection through the GeneXpert MTB/RIF method in patients with suspected TB without previous microbiological documentation.

References

1. WHO operational handbook on tuberculosis. Module 3: diagnosis - rapid diagnostics for tuberculosis detection. Geneva: World Health Organization; 2020. Licence: CC BY-NC-SA 3.0 IGO. (https://www.who.int/publications/i/item/who-consolidated-guidelines-on-tuberculosis-module-3-diagnosis-rapid-diagnostics-for-tuberculosis-detection) Mondoni M, Repossi A, Carlucci P, et al. Bronchoscopic techniques in the management of patients with tuberculosis. Int J Infect Dis. 2017; 64: 27-37.

2. Herráez O, Asencio-Egea M, Huertas M, et al. Cost-effectiveness study of the microbiological diagnosis of tuberculosis using geneXpert MTB/RIF(®). JM.Enferm Infecc Microbiol Clin. 2017; 35: 403-10.

3. Mondoni M, Repossi A, Carlucci P, Centanni S, Sotgiu G. Bronchoscopic techniques in the management of patients with tuberculosis. Int J Infect Dis. 2017; 64: 27-37.

4. Herráez O, Asencio-Egea M, Huertas M, et al. Estudio de coste-efectividad del diagnóstico microbiológico de tuberculosis mediante geneXpert MTB/RIF®. Enferm Infecc Microbiol Clin. 2017; 35: 403-10.

5. Du Rand IA, Blaikley J, Booton R, et al. British Thoracic Society guideline for diagnostic flexible bronchoscopy in adults: accredited by NICE. Thorax 2013; 68 (Suppl 1): i1-i44.

6. Prakash UBS, Kato H. The flexible bronchoscope. In: Prakash U B S, editor. Bronchoscopy. New York: Raven Press, 1994: 156-157.

7. Castella J, Ancochea J, Llorente L, et al. Normativa SEPAR: lavado broncoalveolar. Arch Bronconeumol 1997; 33: 515-26.

8. De Gracia J, Curull V, Vidal R, et al. Diagnostic value of bronchoalveolar lavage in suspected pulmonary tuberculosis. Chest 1988; 93: 329-32.

9. Jafari C, Kessler P, Sotgiu G, et al. Impacto de una Mycobacterium tuberculosis ensayo de liberación de interferón γ específico de en líquido de lavado broncoalveolar para un diagnóstico rápido de tuberculosis. J Intern Med 2011; 270: 254-6.

10. Le Palud P, Cattoir V, Malbruny B, et al. Estudio observacional retrospectivo de precisión diagnóstica de la Xpert® MTB / RIF ensayo en fibra óptica broncoscopia de muestreo para el diagnóstico precoz de los pacientes frotis negativo de esputo o con escasez con sospecha de tuberculosis. BMC Pulm Med. 2014; 14: 137.

11. Tueller C, Chhajed PN, Buitrago-Tellez C, Frei R, Frey M, Tamm M. Value of smear and PCR in bronchoalveolar lavage fluid in culture positive pulmonary tuberculosis. Eur Respir J. 2005; 26: 767-72.

12. Mondoni M, Sotgiu G, Bonifazi M, et al.Transbronchial needle aspiration in peripheral pulmonary lesions: a systematic review and meta-analysis. Eur Respir J. 2016; 48: 196-204.

13. Chen N, Liu Y, Tsao T, et al. Combined bronchoalveolar lavage and polymerase chain reaction in the diagnosis of pulmonary tuberculosis in smear-negative patients. Int J Tuberc Lung Dis. 2002; 6: 350-5.

14. Lee JE, Lee BJ, Roh EY, Kim DK, Chung HS, Lee CH. La precisión diagnóstica del análisis de reacción en cadena de la polim­erasa en tiempo real de la tuberculosis de muestras de lavado bronquial guiadas por tomografía computarizada. Diagnóstico Microbiol Infect Dis. 2011; 71: 51-6.

15. Wong CF, Yew WW, Chan CY, Au LY, Cheung SW, Cheng AF. Rapid diagnosis of smear-negative pulmonary tuberculosis via fibreoptic bronchoscopy: utility of polymerase chain reaction in bronchial aspirates as an adjunct to transbronchial biopsies. Respir Med. 1998; 92: 815-9.

16. Altaf Bachh A, Gupta R, Haq I, Varudkar HG. Diagnosing sputum/smear-negative pulmonary tuberculosis: Does fibre-optic bronchoscopy play a significant role? Lung India. 2010; 27: 58-62.

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