Diagnostic accuracy of GeneXpert MTB/RIF in detecting pulmonary tuberculosis with extremely low loads of MTB in bronchoalveolar lavage fluid in general hospitals

doi:10.19982/j.issn.1000-6621.20240062

Abstract

Abstract:

Objective: To evaluate the accuracy of diagnosing pulmonary tuberculosis (PTB) with extremely low loads of Mycobacterium tuberculosis (MTB) (Ct value >28) in bronchoalveolar lavage fluid by GeneXpert MTB/RIF (BALF-Xpert) in Wuhan general hospitals. Methods: A prospective study was conducted on PTB patients admitted to the Department of Respiratory and Critical Care Medicine of Wuhan Pulmonary Hospital from January 1, 2019 to December 30, 2022, who were referred from 12 general hospitals with extremely low loads of MTB detected by BALF-Xpert. The results of retesting BALF-Xpert, acid-fast bacilli smear microscopy, mycobacterial culture, TB-RNA, and TB-DNA were analyzed. All patients were clinically diagnosed by 3 or more associate professors and followed up for at least 1 year to evaluate the accuracy of BALF-Xpert in detecting MTB with extremely low loads in general hospitals. Results: A total of 67 patients were included. After retesting with BALF-Xpert, 38.81% (26/67) were detected as MTB positive, including 20 cases (76.92%) with extremely low loads, 5 cases (19.23%) with low loads, 1 case (3.85%) with medium loads, and 0 case with high loads of MTB. The positive rate of BALF-Xpert was higher than that of smear microscopy (4.48% (3/67)) and TB-RNA (17.91% (12/67)), with statistically significant difference (χ²=23.280, P=0.001; χ²=7.200, P=0.007). There was no significant difference between BALF-Xpert and culture (29.85% (20/67)) and TB-DNA (25.37% (17/67))(χ²=1.192, P=0.275; χ²=2.774, P=0.096). The total positive rate of combining 5 diagnostic methods was 40.30% (27/67). Forty-three patients were finally diagnosed with tuberculosis and 24 patients were diagnosed as non-tuberculosis disease, with a misdiagnosis rate of 35.82%. Conclusion: BALF-Xpert has a high false positive rate for detection of PTB cases with extremely low loads MTB. A comprehensive diagnosis should be made based on the patient’s clinical manifestations, imaging findings, and immunological results for MTB infection and re-examination is recommended, if necessary.

Key words: Hospital, general, Nucleic acid amplification techniques, Tuberculosis, pulmonary, Diagnosis, Misdiagnosis

CLC Number:

R521

Mei Chunlin, Yang Chengqing, Du Ronghui, Cao Tanze, Feng Wei, Chen Shufang, Liu Xiuping, Ou Jiali. Diagnostic accuracy of GeneXpert MTB/RIF in detecting pulmonary tuberculosis with extremely low loads of MTB in bronchoalveolar lavage fluid in general hospitals[J]. Chinese Journal of Antituberculosis, 2024, 46(9): 1037-1041. doi: 10.19982/j.issn.1000-6621.20240062

Figures/Tables 2

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Xpert检测	例数	涂片镜检		分枝杆菌培养		TB-DNA		TB-RNA		联合检测
Xpert检测	例数	阳性	阴性	阳性	阴性	阳性	阴性	阳性	阴性	阳性	阴性
MTB未检出	41(61.19)	0(0.00)	41(61.19)	1(1.49)	40(59.70)	0(0.00)	41(61.19)	0(0.00)	41(61.19)	1(1.49)	40(59.70)
MTB检出	26(38.81)	3(4.48)	23(34.33)	19(28.36)	7(10.45)	17(25.37)	9(13.43)	12(17.91)	14(20.90)	26(38.81)	0(0.00)
极低	20(29.85)	0(0.00)	20(29.85)	15(22.39)	5(7.46)	13(19.40)	7(10.45)	8(11.94)	12(17.91)	20(29.85)	0(0.00)
低	5(7.46)	2(2.99)	3(4.48)	3(4.48)	2(2.99)	3(4.48)	2(2.99)	3(4.48)	2(2.99)	5(7.46)	0(0.00)
中	1(1.49)	1(1.49)	0(0.00)	1(1.49)	0(0.00)	1(1.49)	0(0.00)	1(1.49)	0(0.00)	1(1.49)	0(0.00)
高	0(0.00)	0(0.00)	0(0.00)	0(0.00)	0(0.00)	0(0.00)	0(0.00)	0(0.00)	0(0.00)	0(0.00)	0(0.00)