title: Incidence and clinical variables associated with streptococcal throat infections: a prospective diagnostic cohort study.
abstract: BACKGROUND
  Management of pharyngitis is commonly based on features which are thought to be associated with Lancefield group A beta-haemolytic streptococci (GABHS) but it is debatable which features best predict GABHS. Non-group A strains share major virulence factors with  group A, but it is unclear how commonly they present and whether their presentation differs.
  
  
  OBJECTIVE
  To assess the incidence and clinical variables associated with streptococcal infections.
  
  
  METHODS
  Prospective diagnostic cohort study in UK primary  care.
  
  
  METHODS
  The presence of pathogenic streptococci from throat swabs was assessed among patients aged ≥5 years presenting with acute sore throat.
  
  
  RESULTS
  Pathogenic streptococci were found in 204/597 patients (34%, 95% CI = 31 to 38%): 33% (68/204)  were non-group A streptococci, mostly C (n = 29), G (n = 18) and B (n = 17); rarely D (n = 3) and Streptococcus pneumoniae (n = 1). Patients presented with similar features whether the streptococci were group A or non-group A. The features best predicting  A, C or G beta-haemolytic streptococci were patient's assessment of severity (odds ratio [OR] for a bad sore throat 3.31, 95% CI = 1.24 to 8.83); doctors' assessment of severity (severely inflamed tonsils OR 2.28, 95% CI = 1.39 to 3.74); absence of a bad cough (OR 2.73, 95% CI  = 1.56 to 4.76), absence of a coryza (OR 1.54, 95% CI = 0.99 to 2.41); and moderately bad or worse muscle aches (OR 2.20, 95% CI = 1.41 to 3.42).
  
  
  CONCLUSIONS
  Non-group A strains commonly cause streptococcal sore throats, and present with similar symptomatic clinical features  to group A streptococci. The best features to predict streptococcal sore throat presenting in primary care deserve revisiting.
authors.affiliation: Primary Care and Population Science, Faculty of Medicine University of Southampton, UK. p.little@soton.ac.uk
authors.forename: Paul
authors.initials: P
authors.lastname: Little
authors.forename: F D Richard
authors.initials: FD
authors.lastname: Hobbs
authors.forename: David
authors.initials: D
authors.lastname: Mant
authors.forename: Cliodna A M
authors.initials: CA
authors.lastname: McNulty
authors.forename: Mark
authors.initials: M
authors.lastname: Mullee
mesh_terms: D000293:Adolescent; D000328:Adult; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D002648:Child; D015331:Cohort Studies; D024881:Drug Resistance, Bacterial; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D018579:Patient Selection; D010612:Pharyngitis / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D011446:Prospective Studies; D012720:Severity of Illness Index; D013290:Streptococcal Infections / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D013297:Streptococcus pyogenes / Q000302:isolation & purification / Q000472:pathogenicity*; D006113:United Kingdom / Q000453:epidemiology
chemical_list: D000900:Anti-Bacterial Agents