A Novel Host-protein Assay Accurately Distinguishes Bacterial From Viral Upper Respiratory Tract Infections
Authors: Oved Kfir , Eden Eran , Van Houten Chantal , Gottlieb Tanya , Navon Roy , Cohen Asi , Boico Olga , Paz Meital , Etshtein Liat , Kronenfeld Gali , Friedman Tom , Bamberger Ellen , Chistyakov Irina , Potasman Israel , Stein Michal , Klein Adi , Gervaix Alain , Srugo Isaac , Bont Louis 
Published: October 2017

Abstract

Background
Bacterial and viral infections are often clinically indistinguishable, particularly in upper respiratory tract infections (URTI), which leads to antibiotic misuse. A novel assay (ImmunoXpert™) that integrates measurements of three host-response proteins (TRAIL, IP-10, CRP) was recently developed to assist in differentiation between bacterial and viral etiologies. We evaluated the assay performance in URTI patients and compared it with standard laboratory measures.

Methods
We performed a sub-analysis of 464 patients with clinical suspicion of URTI enrolled in three previously conducted multi-center clinical studies that evaluated the assay performance in patients with acute infections: ‘Curiosity’ study (NCT01917461), ‘Opportunity’ study (NCT01931254), and ‘Pathfinder’ study (NCT01911143). Comparator method was predetermined criteria combined with expert panel adjudication, which was blinded to the test results. Diagnostic performance was evaluated by comparing test and comparator method outcomes.

Results
A unanimous panel adjudication was attained for 61 bacterial (13%) and 241 viral (52%) patients (162 patients (35%) had an indeterminate diagnosis). The assay distinguished between bacterial and viral infected patients with a sensitivity of 92% (95% CI: 82%- 98%) and specificity of 93% (88%-96%) with 11% equivocal test results. Overall the assay outperformed other routine laboratory tests (FIG 1), including: white blood cell count (WBC; cutoff 15,000 cells/µL, sensitivity 48% (35%-60%), P &lt; 10-−6; specificity 85% (80%-90%), P &lt; 0.05); CRP (cutoff 40 mg/L, sensitivity 82% (72%–92%), P = 0.16, specificity 79% (74%–84%), P &lt; 10-4); Procalcitonin (PCT; cutoff 0.5 ng/mL, sensitivity 22% (11%–32%), P &lt; 10–14, specificity 80% (74%–85%), P &lt; 0.001); absolute neutrophil count (ANC; cutoff 10,000 cells/µL, sensitivity 58% (45%–71%), P &lt; 10-−4, specificity 94% (91%–97%), P = 0.7).

Conclusion
The novel assay demonstrated superior performance compared with routine laboratory tests (WBC, ANC) and biomarkers (CRP, PCT), in distinguishing bacterial from viral etiologies in patients with URTI. It has the potential to help clinicians avoid missing bacterial infections or prescribing unwarranted antibiotics for viral URTIs.

Disclosures
K. Oved, MeMed Diagnostics: Board Member, Employee and Shareholder, Salary E. Eden, MeMed Diagnostics: Board Member, Employee and Shareholder, Salary T. Gottlieb, MeMed Diagnostics: Employee, Salary R. Navon, MeMed Diagnostics: Employee, Salary A. Cohen, MeMed Diagnostics: Employee, Salary O. Boico, MeMed Diagnostics: Employee, Salary M. Paz, MeMed Diagnostics: Employee, Salary L. Etshtein, MeMed Diagnostics: Employee, Salary G. Kronenfeld, MeMed Diagnostics: Employee, Salary T. Friedman, MeMed Diagnostics: Employee, Salary E. Bamberger, MeMed Diagnostics: Employee, Salary I. Chistyakov, MeMed Diagnostics: Consultant, Consulting fee I. Potasman, MeMed Diagnostics: Holding stock options, stock options