title: Validation of the Nasal Mucus Index, a novel measurement of acute respiratory infection severity.
abstract: BACKGROUND
  To assess the concurrent and predictive validity of the Nasal Mucus Index (NMI), a novel measurement of acute respiratory infection (ARI) severity.
  
  
  OBJECTIVE
  ARI, including the common cold and influenza, imposes a great burden on individuals and society. Previous research has attempted to assess the severity of ARI with self-reported and laboratory-based measurements. Self-reported measurements may introduce bias. Laboratory-based metrics are often expensive. Therefore, there is a need for non-self-reported, affordable, and validated ARI severity tests.
  
  
  METHODS
  Participants (N = 719) with an ARI episode underwent nasal lavage on days 1 and 3. The samples were visually assessed for the amount of mucus present in the sample and were given a subsequent NMI score. Collected samples were further assessed for interleukin (IL) 8 values (in pg/mL) and polymorphonuclear neutrophils (PMN) per high-power field. The participants rated episode severity and nasal symptoms daily by using the validated Wisconsin Upper Respiratory Symptom Survey-21 (WURSS-21). A subset of nasal symptoms was used as an additional comparator. NMI scores were compared with same-day IL-8 level, PMN count, and WURSS-21 scores for concurrent validation purposes by using the Spearman ρ as the index of correlation. NMI scores were correlated with overall episode severity measurements to assess predictive validity. Overall episode severity was measured as the WURSS-21 area under the curve, nasal symptoms area under the curve, and episode duration.
  
  
  RESULTS
  The NMI score correlated significantly with the same-day IL-8 level (ρ = 0.443, p < 0.001), PMN count (ρ = 0.498, p < 0.001), WURSS-21 score (ρ = 0.098, p = 0.004), and nasal symptom score (ρ = 0.162, p < 0.001). No significant predictive correlations were found.
  
  
  CONCLUSIONS
  Associations with inflammatory biomarkers and self-reported severity measurements provided evidence of concurrent validity for the novel NMI score. The NMI can be used in future research as a simple, inexpensive, non-self-reported indicator of ARI severity.
authors.affiliation: Department of Family Medicine, Utrecht University, the Netherlands.
authors.forename: Paul M
authors.initials: PM
authors.lastname: Dorresteijn
authors.forename: Daniel
authors.initials: D
authors.lastname: Muller
authors.forename: Yaoguo
authors.initials: Y
authors.lastname: Xie
authors.forename: Zhengjun
authors.initials: Z
authors.lastname: Zhang
authors.forename: Bruce P
authors.initials: BP
authors.lastname: Barrett
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D005260:Female; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009093:Mucus / Q000378:metabolism*; D017817:Nasal Lavage Fluid / Q000276:immunology; D009504:Neutrophils / Q000276:immunology*; D011237:Predictive Value of Tests; D012107:Research Design; D012141:Respiratory Tract Infections / Q000175:diagnosis*; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D055815:Young Adult
chemical_list: D016209:Interleukin-8