title: Evaluation of two Fingerstick blood Point-of-Care Triage Test for Active TB
Creators: name: Gindeh, Awa
Publisher: name: The Open University
Year: 2024

description: <b>Background</b><br>
Tuberculosis (TB) remains a significant global health challenge with about 7.5 million newly diagnosed cases and 1.3 million deaths reported in 2023. This may largely be due to lack of an effective vaccine, poor health system infrastructure and therapeutics.
However, one of the major gaps is lack of fast and accurate diagnostic tests. Hence, the development of fast and accurate sputum independent tests is paramount to combat the global TB epidemic. In this regard, new fingerstick blood tests have been developed by Cepheid (Xpert MTB-HR test) and Leiden University (Multibiomarker test). The Xpert MTB-HR or 3HR test is an RT-PCR test that readily quantifies the messenger RNA (mRNA) transcription levels of 2 host response genes (GBP5, DUSP3) with either KLF2 or TBP as control genes and generates a TB score based on the relative expression levels of these genes. The MBT is a lateral flow-based test that measures the levels of 3 host soluble protein markers SAA1, CRP and IP-10. The aim of this study was to perform prospective analysis of both the 3HR and MBT tests in adults with symptoms suggestive of TB but prior to microbiological confirmation to determine the sensitivity and specificity of both tests in distinguishing TB from other respiratory diseases (ORD).<br><br>
<b>Methods</b><br>
Fingerstick blood (FSB) from individuals presenting with signs and symptoms suggestive of TB was analysed with both 3HR and MBT tests. For the 3HR test, 100ul of FSB was analysed using the Cepheid GeneXpert MTB-HR prototype, while for the MBT, 10ul whole blood or 20ul lysed blood was analysed using the up-converting phosphor (UCP) lateral flow technology. The accuracy of both tests was determined in relation to GeneXpert Ultra and a combinatory microbiological score (GeneXpert Ultra and liquid culture) with patients classified as having either TB or other respiratory diseases (ORDs). CMS classification is such that patients with liquid culture positive and GeneXpert positive greater than trace are classified as definite TB. Both tests were also performed at baseline and after 6-months of anti-TB therapy to determine if the tests can be used for treatment response monitoring.<br><br>
<br>Results<br>
When the 3HR test was evaluated against CMS (n=72 TB; n=106 ORD), there was lower Ct value (higher mRNA input) of all genes and TB score in the TB patients compared to the ORD group. The TB score (TBP, GBP5, DUSP3) discriminated between TB and ORD with AUC of 0.92 (CI 95%; 0.87-0.97) with a sensitivity of 91% and specificity of 81% (CI 95%: 0.82-0.95). The TB score (KLF2, GBP5, DUSP3) also had an AUC of 0.91 with sensitivity of 91% and specificity of 81%. These showed that regardless of the control 
gene used, both meet the WHO TPP requirements for a TB triage test although TBP had a slightly higher AUC. For treatment response monitoring, these showed a significant increase in TB score (lower mRNA) and GBP5 from baseline to 6-months with median [IQR] levels for GBP5 at baseline of 18.60 [17.70-19.30] and 22.10 [21.40-22.90] at 6-months while the median and IQR for the TB score were -3.25 [-1.925- -0.700] at baseline and -1.099[-1.750- -0.8990] at 6-months.<br><br>
Additionally, when the MBT was evaluated against CMS, the test discriminated between TB and ORD with AUC of 0.94 (CI 95%; 0.90-0.98). Setting the sensitivity at 90%, the specificity was 85% (CI 95%; 0.77-0.94). For treatment response monitoring, the MBT 
showed an AUC of 0.73% (CI 95%; 0.61-0.85) with a sensitivity of 92% (CI 95%; 0.78-1.00) and specificity of 53% (CI 95%; 0.44-0.61) from baseline to 6-months of anti-TB treatment.<br><br>
<b>Conclusion</b><br>
The preliminary results from this study showed that both the 3HR test and MBT meet the WHO TPP requirements for a point-of-care Triage TB test using fingerstick blood. The implementation of such diagnostic test in basic health care institutions will help lower the 
TB burden by reducing close contact transmission, giving early diagnosis and reducing the number of confirmatory tests required.