Abstract
Interferon (IFN)-γ release assays (IGRAs) are probably the most accurate tests for the detection of latent Mycobacterium tuberculosis infection, but IGRAs are labour intensive and the transport of samples over longer distances is difficult. IFN-γ-induced protein (IP)-10 is expressed at 100-fold higher levels than IFN-γ, and IP-10 release assays have comparable performance to IGRAs. The aim of this study was to explore the diagnostic potential of a novel IP-10 release assay based on dried plasma spots (DPS).
The presence of IP-10 and IFN-γ was determined in plasma and in DPS by ELISA. Diagnostic algorithms for plasma and DPS tests for IP-10 were developed on a training cohort comprising 60 tuberculosis (TB) patients and 59 healthy controls. Diagnostic accuracy was assessed in a validation cohort comprising 78 TB patients and 98 healthy controls. Plasma was measured in Spain and DPS samples were sent to Denmark using the conventional postal service for analysis.
IP-10 was readily detectable in both plasma and DPS, and correlation was excellent (r2 = 0.95). QuantiFERON-TB Gold In-Tube (QFT-TB) and IP-10 in DPS and plasma rendered comparable sensitivity (78%, 82% and 84%, respectively), specificity (100%, 97% and 97%, respectively) and indeterminate rates (p>0.55).
The DPS-based IP-10 test has comparable diagnostic accuracy to the QFT-TB and samples can be sent via conventional mail over long distances for analysis without affecting the results.
Footnotes
Support statement: This work was supported by the Danish National Advanced Technology Foundation (003-2011-5), the Capital Region of Copenhagen, the Danish Lung Association, the Danish Ministry of Science, Innovation and Higher Education, the Clinical Research Centre at Hvidovre Hospital and the Lundbeck Foundation (R32-A1081) (Denmark). Jose Domínguez is funded by the Miguel Servet programme of the Instituto de Salud Carlos III (Badalona, Spain).
Conflict of interest: Disclosures can be found alongside the online version of this article at www.erj.ersjournals.com
This article was modified in April 2016 to correct errors in the licence information.
- Received August 17, 2012.
- Accepted September 27, 2012.
- ©ERS 2013
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