Increased detection of smear-negative pulmonary tuberculosis by GeneXpert MTB/RIF® assay after bleach concentration

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• 作者：Mulualem Tadesse^a ; ^b ; ^c ; ^{mulualemt.tadesse@gmail.com" class="auth_mail" title="E-mail the corresponding author} ; ^{mulualem.tadesse@ju.edu.et" class="auth_mail" title="E-mail the corresponding author} ; Dossegnaw Aragaw^a ; ^b ; Leen Rigouts^c ; ^d ; Gemeda Abebe^a ; ^b
• 关键词：Bleach concentration ; Diagnostic accuracy ; Smear-negative tuberculosis ; Xpert MTB/RIF
• 刊名：International Journal of Mycobacteriology
• 出版年：2016
• 出版时间：June 2016
• 年：2016
• 卷：5
• 期：2
• 页码：211-218
• 全文大小：316 K

文摘

The GeneXpert MTB/RIF assay (Xpert) was endorsed as the initial diagnostic tool in people suspected of human immunodeficiency virus-associated or drug-resistant tuberculosis (TB). However, information regarding the performance of Xpert for diagnosing smear-negative TB in high burden settings remains limited. We evaluated the diagnostic accuracy of Xpert and the impact of bleach concentration on the performance of Xpert using smear-negative sputum samples from human immunodeficiency virus-negative patients.

Methods

One spot and one morning smear-negative sputum samples per patient were examined using Xpert and culture at the Mycobacteriology Research Center of Jimma University, Ethiopia. The sputum culture on both Löwenstein–Jensen and/or Mycobacteria Growth Indicator Tube was the gold-standard.

Results

Of 185 smear-negative presumptive pulmonary TB cases, 19 (10.3%) had culture-proven TB. The sensitivity of Xpert on spot and morning sputum was similar (63.2%). Testing two specimens per patient insignificantly increased the sensitivity of Xpert. Bleach concentration and pelleting improved the sensitivity of Xpert over unprocessed sputum in paired samples (73.8% vs. 63.2%) without affecting the specificity (95%). Bleach concentration and pelleting allowed an additional seven cases of TB (missed on the first and second direct Xperts) to be detected, five of which were from culture-negative cases.

Conclusion

Testing of a single sputum sample by Xpert can reach reasonable sensitivity and results would be available on the same day, avoiding loss of patients and treatment delay. The sensitivity of Xpert was improved after bleach concentration and pelleting, although its added value needs further study on a larger scale.