Use of IP-10 detection in dried plasma spots for latent tuberculosis infection diagnosis in contacts via mail

R Villar-Hernández,M Ruhwald,B Muriel-Moreno,I Molina-Pinargote,N Altet,J P Millet,E García-García,M L De Souza-Galvão,J Domínguez,I Latorre,J Ruiz-Manzano,Y González-Díaz,J Pilarte,A Cantos,M A Jiménez,C Prat

doi:10.1038/s41598-019-40778-1

Abstract

The aim of this study was to test the use of IP-10 detection in dried plasma from contact studies individuals (contacts of smear positive patients), by comparing it with IP-10 and IFN-γ detection in direct plasma, to establish IP-10 detection in DPS as a useful assay for LTBI diagnosis. Whole blood samples were collected from 80 subjects: 12 with active tuberculosis (TB), and 68 from contact studies. The amount of IFN-γ produced by sensitized T cells was determined in direct plasma by QuantiFERON Gold In-Tube test. IP-10 levels were determined in direct and dried plasma by an in-house ELISA. For dried plasma IP-10 determination, two 25 µl plasma drops were dried in Whatman903 filter paper and sent by mail to the laboratory. Regarding TB patients, 100.0%, 91.7% and 75.0% were positive for IFN-γ detection and IP-10 detection in direct and dried plasma, respectively. In contacts, 69.1%, 60.3% and 48.5% had positive results after IFN-γ and IP-10 in direct and dried plasma, respectively. The agreement among in vitro tests was substantial and IP-10 levels in direct and dried plasma were strongly correlated (r = 0.897). In conclusion, IP-10 detection in dried plasma is a simple and safe method that would help improve LTBI management.

Highlights

Tuberculosis (TB) still causes high morbidity and mortality rates worldwide
Blauenfeldt et al found that inducible protein 10 (IP-10) mRNA isolated from dried blood spots and IP-10 isolated from dried plasma spots (DPS) had higher levels in active TB patients compared to uninfected controls[20]
Regarding Latent tuberculosis infection (LTBI) diagnosis, we previously described the stability of IP-10 in DPS from active TB patients and non-infected individuals, showing that, IP-10 levels detected in DPS are stable and comparable to those detected in direct plasma[18]

Summary

Introduction

Tuberculosis (TB) still causes high morbidity and mortality rates worldwide. The key to disease control is early diagnosis and efficient treatment regimens[1]. Interferon (IFN)-γ release assays (IGRAs), which measure T-cell-mediated responses after specific Mycobacterium tuberculosis antigen stimulation either from whole blood (QuantiFERON technology; QFN, Qiagen, Düsseldorf, Germany) or peripheral blood lymphocytes (T-SPOT.TB; Oxford Immunotec Limited, Abingdon, UK)[3,4,5], have appeared as an alternative for the TST. Having procedures that make sample transportation from the extraction/collection sites to the laboratory simple and safe, and that detect infection markers other than IFN-γ, would be of use, easing IGRA implementation, and improving LTBI control An example of these procedures, is the dried blood and plasma drops. Due to this knowledge gap, the main objective of this study is to test the use of IP-10 detection in dried plasma from contact studies individuals (contacts of smear positive patients), by comparing it with IP-10 and IFN-γ detection in direct plasma, to establish IP-10 detection in DPS as a useful assay for LTBI diagnosis

Objectives

Methods

Results

Conclusion