Comparison of different diagnostic modalities for isolation of <i>Mycobacterium Tuberculosis</i> among suspected tuberculous lymphadenitis patients

Sharif, N.; Ahmed, D.; Mahmood, R. T.; Qasim, Z.; Khan, S. N.; Jabbar, A.; Khattak, A. A.; Asad, M. J.; Ahmed, W.; Khan, M. M.; Awan, U. A.; Zaman, N.; Habiba, U.; Noureen, S.; Alghamdi, H. A.

doi:10.1590/1519-6984.244311

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Brazilian Journal of Biology

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Original Article • Braz. J. Biol. 83 • 2023 • https://doi.org/10.1590/1519-6984.244311 copy

Comparison of different diagnostic modalities for isolation of Mycobacterium Tuberculosis among suspected tuberculous lymphadenitis patients

Comparação de diferentes modalidades de diagnóstico para isolamento de Mycobacterium tuberculosis entre pacientes com suspeita de linfadenite tuberculosa

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Tuberculosis is a communicable disease with high morbidity and mortality rates in developing countries. The study's primary objective is to compare conventional methods such as acid-fast bacillus (AFB) culture and microscopy with rapid diagnostic methods. The secondary objective is to compare histopathological and microbiological findings in suspected patients with tubercular lymphadenitis. A total of 111 samples (August 2018 to September 2019) of lymph nodes were processed for AFB microscopy, AFB cultures, drug-susceptibility testing (DST), histopathology, and Xpert Mycobacterium Tuberculosis (MTB)/resistance to Rifampin (RIF) assays. Out of 111 lymph node samples, 6 (5.4%) were positive for AFB smear microscopy, 84 (75.6%) were positive for AFB culture, 80 (70.7%) were positive on Gene Xpert, and 102 (91.8%) were indicative of tuberculosis for histopathology studies. Mycobacteria growth indicator tube (MGIT) culture positivity was 84 (75.6%) higher than solid Lowenstein-Jensen (LJ) culture 74 (66.6%). Positive cultures underwent phenotypic DST. Two cases were Multidrug-resistant (MDR) on DST, while three cases were Rifampicin resistant on Gene Xpert. The sensitivity of Genexpert was (62%) against the conventional AFB culture method. The poor performance of conventional lymphadenitis diagnostic methods requires early and accurate diagnostic methodology. Xpert MTB/RIF test can help in the treatment of multidrug-resistant TB cases. Nonetheless, rapid and conventional methods should be used for complete isolation of Mycobacterium tuberculosis.

Keywords:
DST: Drug Susceptibility Testing; MGIT: Mycobacterium Growth Indicator Tube; LJ: Lowenstein-Jensen; EPTB: Extra-pulmonary Tuberculosis; ZN: Ziehl-Neelsen

	Parameters	Count (%)
Age	Years, median	23 (15-40 years)
Gender	Female, n (%)	56 (51.5)
	Male, n (%)	55 (49.5)
	Weight loss, n (%)	60(54)
	Fever, n (%)	72 (65)
Lymph node site, n (%)	Cervical	90 (81)
	Cervical and Auxiliary	11 (9.9)
	Cervical and inguinal	10 (9)
Type of node	Unilateral, n (%)	90 (81)
Type of node	Bilateral, n (%)	21 (19)
ESR	mm/h, median	35 (20-65)
Abnormal chest X-ray	Parenchymal	27 (24.3)
	Mediastinal	34 (30.6)
	Hilar	12 (10.8)
	Effusion	2 (1.8)

		Histopathological Results		Total	p-value	Sensitivity	PPV	Overall diagnostic Accuracy (95% CI)
		Not Tuberculous lymphadenitis	Tuberculous lymphadenitis	n (%)		Specificity	NPV
		n (%)	n (%)			Specificity	NPV
AFB Smear	-ve	9	6	15	0.454	5.9	100	94.5
	+ve	0	96	96		100	100
	Total	9	102	111		100	8.6
Gene Xpert	MTB not detected	2	29	31	0.691	71.6	91.2	67.5
	MTB detected	7	73	80		71.6	91.2
	Total	9	102	111		22.2	6.5
AFB Culture	Negative	8	29	37	0.000	71.6	98.6	73
	Positive	1	73	74		71.6	98.6
	Total	9	102	111		89	21.6

Test Result Variable(s)	Area	Std. Error^a a Under the nonparametric assumption;	Asymptotic Sig.^b b Null hypothesis: true area = 0.5.	Asymptotic 95% Confidence Interval
Test Result Variable(s)	Area	Std. Error^a a Under the nonparametric assumption;	Asymptotic Sig.^b b Null hypothesis: true area = 0.5.	Lower Bound	Upper Bound
FM Stain Results	.529	.096	.771	.341	.717
Xpert MTB Result	.469	.098	.758	.277	.661
culture L J	.802	.068	.003	.668	.936
culture MGIT	.767	.108	.008	.555	.978

		Culture LJ		Total
		Negative	Positive	Total
Culture MGIT	Contamination	1	3	4
	Negative	9	14	23
	Positive	27	57	84
Total		37	74	111

Description	B1	B2	B3	B4	B5
AFB Culture +ve	44(39.6%)	22(19.81)	1(0.9%)	6(5.4%)	1(0.9%)
Gene Xpert: MTB detected	50(45%)	17(15.31)	5(4.5%)	5(4.5%)	1(0.9%)
AFB smear +ve	2(1.8%)	2(1.8%)	1(0.9%)	1(0.9%)	0(0%

		AFB Culture		Total	p-value	Sensitivity	PPV	Overall Diagnostic Accuracy (95% CI)
		Negative	Positive	Total	p-value	Specificity	NPV	Overall Diagnostic Accuracy (95% CI)
AFB Smear	Smear –ve	34	71	105	0.374	4.1	50	33
	Smear +ve	3	3	6		4.1	50
	Total	37	74	111		91.9	32.4
Gene Xpert	MTB not detected	5	26	31	0.017	64.9	60	48
	MTB detected	32	48	80		13.5	16.1
	Total	37	74	111		13.5	16.1

Drug Susceptibility Testing Profile
	Frequency	Percent
Mono_R (INH)	3	2.7
Mono_R (OFX)	1	.9
Mono_R (PZA)	7	6.3
Mono_R (RIF)	1	.9
Mono_R (STREP)	2	1.8
NA	22	19.8
Pan-S (N)	75	67.6
Total	111	100.0

		Xpert Rifampicin Resistance				Total
		NA	RRD	RRID	RRND	Total
DST Profile	Mono_R (INH)	1	1	0	1	3
	Mono_R (OFX)	1	0	0	0	1
	Mono_R (PZA)	3	0	0	4	7
	Mono_R (RIF)	0	1	0	0	1
	Mono_R (STREP)	0	0	0	2	2
	NA	0	0	0	22	22
	Pan-S	28	1	1	45	75
Total		33	3	1	74	111

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