Role of CBNAAT in Diagnosis of Tubercular Pleural Effusion

Dr.Sahil Nayee *¹, Dr.Sanjay Tripathi², Dr.Vishakha Kapadia³, Dr.Rajdeep Dhandhukiya⁴, Dr. Krupa Shah⁵

1. Dr.Sahil Nayee (2nd Year Resident Respiratory Medicine) NHLMMC Ahmedabad

2. Dr.Sanjay Tripathi (HOD, PG Teacher)

3. Dr.Vishakha Kapadia (Associate Professor)

4. Dr.Rajdeep Dhandhukiya (Assistant Professor)

5. Dr.Krupa Shah (3rd Year Resident Respiratory Medicine)

*Correspondence to:  Dr. Sahil Nayee, 2nd Year Resident Respiratory Medicine, NHLMMC Ahmedabad.

Copyright

© 2024 Dr. Sahil Nayee. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Received: 11 Oct 2024

Published: 23 Oct 2024

Abstract:

India is presently one of the high burden countries for tuberculosis and accounts for 23% of global TB burden with 2.2 million patients. Of these reported cases in India around 20% are of Extra Pulmonary Tuberculosis (EPTB).Pleural effusion due to TB is currently the second common location for EPTB next to TB lymphadenitis. The bacteriological confirmation to diagnose EPTB is more difficult due to its paucibacillary nature. The present study was done to determine the role of  CBNAAT  being rapid and non-invasive diagnostic methods for early detection of tuberculous pleuritis, which is essential for treatment initiation, improved patient outcome and for more effective public health intervention.

Introduction

•Pleural effusion is the accumulation of fluid in between the parietal and visceral pleura, called the pleural cavity. It can occur by itself or can be the result of surrounding parenchymal disease like infection, malignancy, or inflammatory conditions.

•Pleural effusion is one of the major causes of pulmonary mortality and morbidity. According to the global TB report of the World Health Organization, a total of 10.0 million people were infected with the disease in 2018.

•India being in the high TB burden, accounts for 27% of the world's TB cases with an estimated 27.5 lakhs patients as per Global TB report 2018. TB can involve any organ in the body, with pulmonary TB being the most common. Pleural effusion due to TB is currently the most common location for Extra Pulmonary Tuberculosis (EPTB) next to lymph node TB.

•Major hindrances for diagnosing EPTB are due to variable clinical presentation and lack of standardized laboratory methods. Early detection of TB and drug resistance is important in the management of TB. The diagnosis is compromised due to the paucibacillary nature of disease in extra pulmonary specimens.

 

CBNAAT- cartridge based nucleic acid amplification test

•The rapid, fully automated NAAT also known as Xpert MTB/RIF assay –has been described as a major breakthrough in TB control and program. The GeneXpert is currently the only one of its kind using a cartridge containing lyophilized reagents, buffers, and washes. The Xpert MTB/RIF assay is based on hemi-nested real-time PCR amplifying the rpoB gene target.

 

•The original WHO policy guidance on Xpert MTB/RIF(2010) advises its use as the diagnostic test in individuals suspected of having multidrug-resistant TB or HIV associated TB. In 2013 updated policy, it recommended Xpert MTB/RIF for the diagnosis of EPTB, for suspected cases of pulmonaryTB (conditional recommendations) and TB in children

 

CBNAAT Testing involves three manual steps:

1. Addition of sample treatment reagent to liquefy and inactivate the bacteria in the sputum.

2. Transfer of 2ml of liquefied sputum into the cartridge.

3. Loading of the cartridge into the device for the assay  All further steps are automated.

 

The role of CBNAAT for early diagnosis of tubercular effusion has been evaluated as an alternative diagnostic tool with an added advantage to detect rifampicin resistance.

 

Adenosine deaminase (ADA)

A key enzyme in purine metabolism, converting adenosine and deoxyadenosine into inosine and deoxyinosine. It is crucial for maintaining cellular purine balance and is particularly important in lymphoid tissues. ADA regulates lymphocyte function by detoxifying deoxyadenosine, which can be toxic if accumulated.

 

Clinical Significance:

Diagnostic Marker:

Elevated ADA levels are used to diagnose tuberculosis (TB) in pleural effusion and peritoneal dialysis fluid, reflecting an inflammatory response consistent with active TB.

 

Genetic Disorders:

 ADA deficiency is associated with severe combined immunodeficiency (SCID), a genetic disorder that severely impairs immune function and increases infection risk.

ADA activity is measured in biological fluids such as serum and pleural fluid, aiding in disease diagnosis and treatment monitoring.

 

Materials and Methods

A retrospective study on 46 patients presenting with symptoms, medical history, radiological picture suggestive of pleural effusion, either admitted or attending OPD of Department of Department of respiratory medicine were enrolled in the study.

 

Inclusion criteria

We included the patients aged >18 years with a medical history suggestive of pleural effusion, Patients with pleural effusion were identified by-Clinical examination, chest x-ray, ultrasonography, and diagnostic thoracocentesis for fluid analysis showing exudative nature of pleural fluid.

 

 Exclusion criteria

1. Patients age<18 yrs.

2. Transudative pleural effusions.

3. Hemothorax (hemorrhagic pleural effusion), Empyema.

4. Inadequate Pleural Fluid Reports.

 

Methodology

In a retrospective review of 46 pleural effusion cases, we analyzed medical histories and clinical examinations to assess the diagnostic approach. The data included details on diagnostic thoracocentesis performed under aseptic conditions. Pleural fluid samples were subjected to a range of tests: biochemical assays for sugar, protein, LDH, and ADA levels, as well as microbiological evaluations - CBNAAT. Additionally, the differential count of the pleural fluid was examined.

 

In the study, presence of ≥two of the following criteria was adopted to label a case as tuberculous

1. Bacteriological confirmation of the presence of Mycobacterium tuberculosis in pleural fluid CBNAAT

2. Clinical presentation consistent with TB with the exclusion of other clinical considerations;

3. Exudative (according to Light’s criteria), lymphocytic pleural effusion .

4. ADA ≥ 40 IU/L

In a retrospective analysis of pleural fluid data from 46  patients were initiated on standard anti-tubercular treatment for pleural tuberculosis under the National Tuberculosis Elimination Program (NTEP). After six months, the clinical and radiological outcomes of the 46 patients were reassessed to evaluate the effectiveness of the treatment.

 

 Observation and Results

Age wise distribution of study population (n-46)

Age Group(n-46)	Females	Males	%
18-30	5	8	28.26%
31-40	2	6	17.39%
41-50	3	4	15.21%
51-60	1	6	15.21%
>60	4	7	24%
TOTAL	15(32%)	31(68%)	100%

Symptoms at presentation

Dry Cough	32(70%)
Fever	31(68%)
Chest Pain	23(50%)
Shortness Of Breath	29(62%)
Loss Of Appetite	16(35%)
Loss Of Weight	14(31%)
Cough With Expectoration	3(6%)

 

ADA and CBNAAT in study

	NO.OF CASES	CBNAAT MTB DETECTED	CBNAAT MTB NOT DETECTED
ADA >40 IU/L	32	6	26
ADA <40 IU/L	14	2	12
TOTAL	46	8	38

 

Pleural fluid lymphocyte wise ada and cbnaat in study population

LYMPHOCYTES(%) (n 46)	TOTAL NUMBER OF CASES	ADA		CBNAAT
		>40 IU/L(n 32)	<40IU/L(n 14)	MTB  DETECTED (n 8)	MTB NOT DETECTED(n 38)
60-70	12	6	6	3	9
71-80	13	9	4	4	9
81-90	11	9	2	1	10
91-100	10	8	2	0	10

 

Association Between Sputum Smear Results and Pleural Fluid CBNAAT Results:

N=14	PLEURAL FLUID CBNAAT RESULT
SPUTUM SMEAR		POSITIVE	NEGATIVE
	SMEAR POSITIVE	1	3
	SMEAR NEGATIVE	7	3

 

A p-value of 0.478 indicates that there is no statistically significant association between sputum smear positivity and pleural fluid CBNAAT results. This suggests that the distribution of CBNAAT results does not significantly differ based on the sputum smear results. In other words, the likelihood of a positive or negative CBNAAT result is not meaningfully influenced by whether the sputum smear is positive or negative. The observed data is consistent with the possibility that any differences are due to random chance rather than a true relationship between sputum smear status and CBNAAT outcomes.

 

Clinical and Radiological Outcome at the end of 6th Month of Treatment

Radiological Improvement Based on CBNAAT Results in Patients with Pleural Tuberculosis

n=46	RADIOLOGICAL
CBNAAT		IMPROVEMENT PRESENT	IMPROVEMENT ABSENT
	POSITIVE	6	2
	NEGATIVE	33	5

 

The p-value obtained from Fisher's Exact Test is approximately 0.0202. This p-value is less than the commonly used significance level of 0.05.

The analysis indicates a significant relationship between CBNAAT results and radiological improvement, suggesting that positive CBNAAT results are associated with better radiological outcomes.

 

CBNAAT RESULTS (n 8)	R -RESISTANCE NOT DETECTED	R -RESISTANCE DETECTED
	6	2

Based on the CBNAAT results from the table, 6 patients showed no resistance (R resistance), while 2 patients exhibited resistance.

 

 Clinical Improvement Based on CBNAAT Results in Patients with Pleural Tuberculosis

N-46	CLINICAL
CBNAAT		IMPROVEMENT PRESENT	IMPROVEEMNT ABSENT
	POSITIVE	7	1
	NEGATIVE	35	3

 

CBNAAT to Clinical

The p-value obtained from Fisher's Exact Test is approximately 0.0027, which is below the commonly used significance threshold of 0.05.

The analysis demonstrates a significant relationship between CBNAAT results and clinical improvement. Positive CBNAAT results are associated with an increased likelihood of clinical improvement, which can aid in better predicting patient outcomes and guiding clinical decisions.

 

Relationship between Clinical and Radiological Improvement

	RADIOLOGICAL IMPROVEMENT
CLINICAL IMPROVEMENT		PRESENT	ABSENT
	PRESENT	37	5
	ABSENT	2	2

The p-value obtained from Fisher's Exact Test is approximately 0.0066, which is significantly lower than the commonly used significance level of 0.05.

The analysis reveals a robust and statistically significant link between radiological and clinical improvement. This suggests that radiological improvements are strongly associated with clinical improvements, providing valuable insight into patient prognosis and treatment evaluation.

 

Discussion

DATA	OUR STUDY	R.SHRINIDHI et al	MODI  et al	KATE  et al	CHAKRABORTHY  et al	ZAINUL  et al
M:F RATIO	68%	80%	73.33%	72%	-	-
AGE GROUP  (YEARS)	18-30(28.26%)	18-30 (36%)	18-30(40%)	-	-	-
MEAN AGE(YEARS)	43.08	39.88	43.19	-	-	45.17
CLINICAL PRESENTATION
DRY COUGH	32(70%)	-			67(89%)
FEVER	31(68%)	68(68%)			57(76%)
CHEST PAIN	23(50%)	78(78%)			46(61%)
SHORTNESS OF BREATH	29(62%)	65(65%)			42(56%)
LOSS OF APPETITE	16(35%)	56(56%)			31(41%)
LOSS OF WEIGHT	14(31%)	34(34%)			28(37%)
COUGH WITH EXPECTORATION	3(6%)	-			14(18.7%)
-LYMPHOCYTE PREDOMINANCE	65.31%	74%	67.87%	90%	-	-
ADA >40 IU/L	69.56%	70%	72.38%	93.33%	-	-
CBNAAT POSITIVITY	17.39%	30%	-	-	32%	31%
CBNAAT SENSITIVITY	19.15%	40%	-	-	-	40.7%
CBNAAT SPECIFICITY	100%	82%	-	-	-	86.6%

 

In comparing our study with those conducted by R. Shrinidhi et al., Modi et al., Kate et al., Chakraborthy et al., and Zainul et al., several key findings emerge. Our study showed a male-to-female ratio of 68%, which is lower than the 80% observed by Shrinidhi et al. and comparable to the 73.33% reported by Modi et al.

The age group analysis revealed that 28.26% of our patients were aged 18-30 years, which is lower compared to the 36% reported by Shrinidhi et al. and 40% by Modi et al.

Our mean age was 43.08 years, aligning closely with Modi et al.'s 43.19 years but higher than Zainul et al.'s mean age of 45.17 years.

In terms of clinical presentation, our study found 70% of patients experienced dry cough, which is lower than the 89% reported by Kate et al. Fever was noted in 68% of our patients, consistent with the 68% reported by Shrinidhi et al. but lower than Kate et al.'s 76%. Chest pain was observed in 50% of our patients, lower than Shrinidhi et al.'s 78% and Kate et al.'s 61%. Shortness of breath was present in 62% of our cohort, slightly higher than the 65% reported by Shrinidhi et al. but lower than Kate et al.'s 56%. Loss of appetite and weight loss were reported in 35% and 31% of our patients, respectively, which is less compared to Shrinidhi et al.’s 56% and 34%, respectively, but similar to or slightly higher than the rates reported by Kate et al.

Our study showed lymphocyte predominance in 65.31% of pleural fluids, lower than the 74% reported by Shrinidhi et al. and 90% by Kate et al.

 ADA levels greater than 40 IU/L were found in 69.56% of our cases, which is comparable to Shrinidhi et al.'s 70% and lower than Kate et al.'s 93.33%. 

CBNAAT positivity in our study was 17.39%, lower than the 30% reported by Shrinidhi et al., Chakraborthy et al.'s 32% and Zainul et al.'s 31%. Our CBNAAT sensitivity was 19.15%, which is lower than Shrinidhi et al.'s 40% and Zainul et al.'s 40.7%, but with perfect specificity of 100%, higher than Shrinidhi et al.'s 82% and Zainul et al.'s 86.6%.

Overall, while our study shares some similarities with existing literature, particularly in high CBNAAT specificity, there are distinct differences in clinical presentation and Demography.

 

Conclusion

Diagnosing tubercular exudative pleural effusion is a complex challenge requiring a thorough diagnostic approach. Effective management hinges on integrating patient history, physical examination, blood tests, fluid analysis, ADA levels, and CBNAAT. Relying on a single test may fall short, underscoring the need for a comprehensive evaluation. Elevated ADA levels (>40 IU/L) are strongly linked to positive CBNAAT results, which in turn correlate with better radiological (p=0.0202) and clinical outcomes (p=0.0027). A robust correlation exists between radiological and clinical improvements (p=0.0066), reinforcing the critical role of CBNAAT in evaluating patient outcomes.  

 

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