Evaluation of the GeneXpert MTB/RIF to diagnose tuberculosis in a public health laboratory

Arbués, Mohanna Damasceno; Rossetti, Maria Lúcia Rosa

doi:10.11606/s1518-8787.2024058005306

Brasil

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Original Article • Rev. Saúde Pública 58 • 2024 • https://doi.org/10.11606/s1518-8787.2024058005306 linkcopy

Evaluation of the GeneXpert MTB/RIF to diagnose tuberculosis in a public health laboratory

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

OBJECTIVES To evaluate the performance of geneXpert MTB/Rif versus conventional methods (bacilloscopy and culture) in the diagnosis of tuberculosis in a Central Public Health Laboratory (LACEN, Tocantins), Northern Brazil.

METHODS Retrospective study, with information from 1,973 suspected cases of tuberculosis from patients treated from January 2015 to December 2020.

RESULTS From the culture (reference standard), the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the geneXpert MTB/Rif were 100%, 97%, 74%, 100%, and 97%, respectively, against 85%, 98%, 80%, 98%, and 97% of bacilloscopy.

CONCLUSIONS The geneXpert MTB/Rif performed similarly to culture and better than bacilloscopy. Although positive cases with negative culture should be evaluated with caution, its routine use is important for the early detection of tuberculosis.

Tuberculosis; Mycobacterium Tuberculosis; Clinical Laboratory Techniques

Characteristic	Bacilloscopy			Culture			GeneXpert MTB/Rif

	Positive	Negative	p-value^a	Positive	Negative	p-value^a	Positive	Negative	p-value^a

	n (%)	n (%)		n (%)	n (%)		n (%)	n (%)
Sex			0.19			0.03			0.02
Male	91 (63.6)	1,064 (58.1)		102 (66.7)	1,053 (57.9)		135 (65.9)	1,020 (57.7)
Female	52 (36.4)	766 (41.9)		51 (33.3)	767 (41.1)		70 (34.1)	748 (42.3)
Age range			0.01			0.01			0.01
0–20	14 (9.8)	163 (8.9)		11 (7.2)	166 (9.1)		20 (9.8)	157 (8.9)
21–40	62 (43.4)	617 (33.7)		69 (45.1)	610 (33.5)		85 (41.5)	594 (33.6)
41–60	45 (31.5)	536 (29.3)		47 (30.7)	534 (29.3)		64 (31.2)	517 (29.2)
61–80	19 (13.3)	437 (23.9)		22 (14.4)	434 (23.8)		32 (15.6)	424 (24)
81–100	3 (2.1)	77 (4.2)		4 (2.6)	76 (4.2)		4 (2)	76 (4.3)
Ethnicity			< 0.01			0.02			< 0.01
Indigenous	13 (9.1)	64 (3.5)		11 (7.2)	66 (3.6)		20 (9.8)	57 (3.2)
Other	130 (90.9)	1,766 (96.5)		142 (92.8)	1,754 (96.4)		185 (90.2)	1,711 (96.8)

Characteristic	Culture			Sensitivity	Specificity	PPV	NPV	Accuracy

	Positive	Negative	p-value^a

	n (%)	n (%)		% (95%CI)	% (95%CI)	% (95%CI)	% (95%CI)	% (95%CI)
GeneXpert MTB/Rif
Positive n (%)	153 (100)	53 (2.9)	< 0.01	100 (97.6–100.0)	97.1 (96.2–97.8)	74.7 (68.9–79.0)	100 (99.6–100.0)	97.3 (96.5–97.9)
Negative n (%)	0 (0)	1,767 (97.1)	< 0.01	100 (97.6–100.0)	97.1 (96.2–97.8)	74.7 (68.9–79.0)	100 (99.6–100.0)	97.3 (96.5–97.9)
Bacilloscopy
Positive n (%)	122 (80.3)	21 (1.2)	< 0.01	85.3 (78.4–90.7)	98.4 (97.7–99.0)	80.3 (73.9–85.4)	98.8 (98.3–99.2)	97.4 (6.6–98.1)
Negative n (%)	30 (19.7)	1,800 (98.8)	< 0.01	85.3 (78.4–90.7)	98.4 (97.7–99.0)	80.3 (73.9–85.4)	98.8 (98.3–99.2)	97.4 (6.6–98.1)
GeneXpert MTB/Rif
Baciloscopy				96.5 (92.0–98.9)	96.2 (92.2–97.0)	66.7 (61.3–71.6)	99.7 (99.3–99.9)	96.2 (95.3–97.0)
Positive n (%)	138 (66.7)	5 (0.3)	< 0.01
Negative n (%)	69 (33.3)	1,761 (99.7)

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Faculdade de Saúde Pública da Universidade de São Paulo Avenida Dr. Arnaldo, 715, 01246-904 São Paulo SP Brazil, Tel./Fax: +55 11 3061-7985 - São Paulo - SP - Brazil
E-mail: revsp@usp.br

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[TFN1] MTB: Mycobacterium tuberculosis.

[TFN2] ^a p-value: p ≤ 0.05.