title: The minimally important difference in the Rhinoconjunctivitis Total Symptom Score in grass-pollen-induced allergic rhinoconjunctivitis.
abstract: BACKGROUND
  The minimally important difference (MID) has been defined as the smallest improvement considered worthwhile by a patient. The MID has not been estimated for the Rhinoconjunctivitis Total Symptom Score (RTSS).
  
  
  METHODS
  In a prospective multicentre study, patients consulting for grass-pollen-induced allergic rhinitis (AR) recorded a 15-point global rating of change scale (GRCS) score and the Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ) score on a weekly basis and the individual symptom scores comprising the RTSS on a daily basis over two consecutive weeks. The MID in the RTSS was determined with anchor-based methods (using the GRCS and the RQLQ) and a distribution-based method [based on the RTSS' standard deviation (SD)].
  
  
  RESULTS
  The study population comprised 806 patients (253 children, 250 adolescents and 303 adults). During the first week of the study, the mean ± SD RTSSs for these age groups were 6.5 ± 3.3, 6.8 ± 3.4 and 7.0 ± 3.4, respectively. For an improvement of 2 points in the GRCS or 0.5 points in the RQLQ score, the regression analysis yielded MIDs in the RTSS of 1.24 ± 0.17 and 1.12 ± 0.14 in children, 1.33 ± 0.14 and 1.20 ± 0.13 in adolescents and 1.13 ± 0.14 and 0.89 ± 0.12 in adults, respectively. When applying distribution-based methods, the MID ranged from 1.09 to 1.13 (based on 0.33 SDs of the first-week RTSS) and from 1.22 to 1.40 (based on 0.5 SDs of the difference in RTSSs between the first and second weeks).
  
  
  CONCLUSIONS
  The MID in the RTSS was consistently estimated as 1.1-1.3 (and could conceivably be rounded to 1) in patients with grass-pollen-induced AR.
authors.affiliation: UPRES EA 220, Hôpital Foch, Université Versailles Saint-Quentin, Suresnes, France; Délégation à la Recherche Clinique et à l'Innovation, Unité de Méthodologie, Hôpital Foch, Suresnes, France.
authors.forename: P
authors.initials: P
authors.lastname: Devillier
authors.forename: O
authors.initials: O
authors.lastname: Chassany
authors.forename: E
authors.initials: E
authors.lastname: Vicaut
authors.forename: O
authors.initials: O
authors.lastname: de Beaumont
authors.forename: B
authors.initials: B
authors.lastname: Robin
authors.forename: J F
authors.initials: JF
authors.lastname: Dreyfus
authors.forename: P J
authors.initials: PJ
authors.lastname: Bousquet
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000485:Allergens / Q000276:immunology*; D002648:Child; D002675:Child, Preschool; D015897:Comorbidity; D003233:Conjunctivitis, Allergic / Q000175:diagnosis / Q000188:drug therapy / Q000276:immunology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011058:Pollen / Q000276:immunology*; D011446:Prospective Studies; D011788:Quality of Life; D012372:ROC Curve; D012220:Rhinitis / Q000175:diagnosis*; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D055815:Young Adult
chemical_list: D000485:Allergens
keywords: allergic rhinoconjunctivitis; minimally important difference; symptom score