Diagnostic Performance of Different Laboratory Methods for the Detection of Extrapulmonary Tuberculosis

Abstract

Accurate and appropriate extrapulmonary tuberculosis (EPTB) diagnosis remains challenging due to its paucibacillary nature, requirement of invasive collection procedures, and lack of sensitive tests. This study investigated the diagnostic performance of different methods for the diagnosis of EPTB. A total of 1340 EPTB specimens were collected from presumptive EPTB patients from four different hospitals between November 2015 and March 2017. The collected specimens were tested with AFB microscopy, culture, Xpert MTB/RIF assay (Xpert), and MTBDRplus assay. Among the 1340 EPTB specimens, 49 (3.66%), 141 (10.52%), 166 (12.39%), and 154 (11.49%) were positive in AFB microscopy, culture, Xpert MTB/RIF, and MTBDRplus assay, respectively. A total of 194 (14.9%) cases were found positive in at least one of these methods. Using culture as a reference standard, the sensitivity and specificity of AFB microscopy, Xpert MTB/RIF, and MTBDRplus assay were: 27.0%/99.1%, 83.7%/96.0%, and 79.4%/96.5%, respectively. Compared to the composite reference standard, the sensitivity of culture, AFB microscopy, Xpert MTB/RIF, and MTBDRplus assay was 72.7%, 25.3%, 85.6%, and 79.4%, respectively, with a specificity of 100% for all the methods. The Xpert MTB/RIF assay showed the highest sensitivity compared to other methods. Considering the short turnaround time and promising findings, Xpert MTB/RIF assay should be integrated into national TB guidelines as a routine diagnostic test.

Label-free citrate-stabilized silver nanoparticles-based highly sensitive, cost-effective and rapid visual method for differential detection ofMycobacterium tuberculosisandMycobacterium bovis

“…Hence, microscopy-based detection may lead to false negative cases causing increase in transmission due to lack of timely detection. A recent study compared sensitivity and specificity of M. tb detection in EPTB employing a variety of currently used clinical diagnostic methods and observed only a 25% sensitivity in case of AFB microscopy compared to the state-of-the-art methods, such as culture-based detection (72.7%), Xpert MTB/RIF (85.6%), and MTBDRplus assay (79.4%) with a 100% specificity for all the methods 5 . Culture test, the current gold standard is highly sensitive and specific and can detect as few as 10-100 viable bacilli/ml of the specimen and can detect both PTB, EPTB, and paucibacillary (low bacterial load) cases, which may not be detected by sputum smear microscopy.…”

Label-Free Citrate-Stabilized Silver Nanoparticles-Based, Highly Sensitive, Cost-Effective, and Rapid Visual Method for the Differential Detection of Mycobacterium tuberculosis and Mycobacterium bovis

“…Hence, microscopy-based detection may lead to false negative cases, causing an increase in transmission due to a lack of timely detection. A recent study compared the sensitivity and specificity of M. tb detection in EPTB employing a variety of currently used clinical diagnostic methods and observed only a 25% sensitivity in the case of AFB microscopy compared to the state-of-the-art methods, such as culture-based detection (72.7%), Xpert MTB/RIF (85.6%), and MTBDRplus assay (79.4%) with a 100% specificity for all the methods . Culture test, the current gold standard, is highly sensitive and specific and can detect as few as 10–100 viable bacilli/mL of the specimen and can detect both PTB, EPTB, and paucibacillary (low bacterial load) cases, which may not be detected by sputum smear microscopy.…”