Serum IP-10 as a Biomarker of Human Rhinovirus Infection at Exacerbation of COPD

Abstract

Human rhinovirus (HRV) is the most frequent virus associated with COPD exacerbations. Viral infections increase exacerbation severity and likelihood of hospitalization. As ease of sampling blood makes serum a more practical marker than sputum, we investigated whether changes in serum interferon-gamma-inducible protein 10 (IP-10) from baseline to exacerbation were higher in airway HRV-positive exacerbations and whether IP-10 levels related to HRV load. One hundred thirty-six patients with COPD and 70 controls were included over 2 years and 72 exacerbations sampled. HRV positivity and load were determined by reverse transcriptase-polymerase chain reaction in nasopharyngeal swabs and/or sputum at baseline and exacerbation. IP-10 was measured by enzyme-linked immunosorbent assay in serum and compared with HRV load. At baseline, serum IP-10 was higher in patients with COPD than controls; medians were 149.4 pg/mL (103-215) and 111.7 pg/mL (82-178), P = .02. The presence of HRV at baseline did not increase IP-10: patients with COPD, 166.9 pg/mL (110-240) and 149.4 pg/mL (103-215), P = .30; controls, 136.4 pg/mL (77-204) and 111.7 pg/mL (82-178), P = .53. IP-10 increased significantly from baseline to exacerbation in HRV-positive exacerbations: 154.9 pg/mL (114.0-195.1) to 207.5 pg/mL (142.1-333.5), P = .009. There was no change in IP-10 between baseline and exacerbation in HRV-negative exacerbations: 168.3 pg/mL (94.3-249.8) and 175.6 pg/mL (107.2-290.4), P = .49. At exacerbation, IP-10 correlated with sputum viral load: rho = 0.48; P = .02. In receiver operating characteristics analysis, the combination of IP-10 and coryzal symptoms gave an area under the curve of 0.82 (95% CI, 0.74-0.90). IP-10 increases from baseline to exacerbation in HRV-positive exacerbations and correlates with sputum HRV load. Serum IP-10 may be useful as a novel marker for these events.