title: The use of white blood cell count and left shift in the diagnosis of appendicitis in children.
abstract: BACKGROUND
  The use of white blood cell (WBC) count and left shift in the diagnosis of appendicitis in pediatric patients is unproven. It is commonly thought that children with appendicitis have an elevated WBC count with a left shift; however, most data supporting this belief stem from studies conducted on appendicitis in adults, not children. The purpose of this investigation was to determine the value of WBC count and differential in the diagnosis of appendicitis in children presenting to the emergency department (ED) with acute abdominal pain.
  
  
  METHODS
  Seven hundred twenty-two pediatric ED patients with a primary complaint of nontraumatic abdominal pain were identified by prospective and retrospective methods. White blood cell count with differential was performed on patients with history and physical examination findings that were felt to warrant laboratory investigation. Results of WBC counts were determined as low, normal, or high, with or without a left shift, based on normal age-related values per laboratory protocol for pediatric patients.
  
  
  RESULTS
  The diagnosis of appendicitis was made in 10.2% of all patients presenting to the ED with acute abdominal pain. Thirty percent of toddlers (1-3.9 years) with high WBC counts had appendicitis, whereas 0% of toddlers with low WBC counts and 4.8% of toddlers with normal WBC counts had appendicitis (chi = 6.5, P = 0.04). A normal WBC count did not rule out appendicitis in toddlers; however, the negative predictive value (NPV) for normal or low WBC count was high (NPV = 95.6%). In the child age group (4-11.9 years), high WBC count was both sensitive and specific for the diagnosis of appendicitis in children (sensitivity = 71%, specificity = 72%), and the NPV for normal or low WBC count was high (NPV = 89.5%). Lastly, 43.9% of adolescents (12-19 years) with high WBC counts had appendicitis, whereas 0% of adolescents with low WBC counts and 8.3% of adolescents with normal WBC counts had appendicitis (chi = 37.3, P < 0.001). The NPV for a low or normal WBC count was also high in the adolescent group (NPV = 91.9%). Left shift was also strongly associated with appendicitis. Among toddlers, 40% of patients with a left shift had appendicitis, whereas 1.8% of toddlers without a left shift had appendicitis (chi = 25.7, P < 0.001, NPV = 98.2%). Similarly, left shift was strongly associated with appendicitis in children and adolescents. Among children, 54.3% of patients with a left shift had appendicitis, whereas 5.4% of children without a left shift had appendicitis (chi = 67.8, P < 0.001, NPV = 90.5%). Among adolescents, 53.5% of patients with a left shift had appendicitis, whereas 6.1% of adolescents without a left shift had appendicitis (chi = 72.3, P < 0.001, NPV = 93.9%). In patients with a left shift, 51.2% had appendicitis, whereas 3.7% of patients without a left shift had appendicitis (chi = 226.2; P < 0.001, NPV = 96.3%). In all patients with appendicitis, elevated WBC counts had a sensitivity of 67% and a specificity of 80%. Using left shift alone as an indicator for appendicitis was associated with a sensitivity of 59% and a specificity of 90%. However, when a high WBC count and left shift were combined, the sensitivity climbed to 80%, and specificity remained at 79%. The sensitivity fell to 47% when both a high WBC count and left shift were analyzed, and specificity climbed to 94%. The positive likelihood ratio for a high WBC count and left shift was 9.8.
  
  
  CONCLUSIONS
  The determination of WBC count and differential is useful in the diagnosis of appendicitis in children presenting to the ED with nontraumatic acute abdominal pain, regardless of age. High WBC counts and left shift are independently, strongly associated with appendicitis in children aged 1 to 19 years. In fact, for this subset of patients older than 4 years, the most common diagnosis in the setting of an elevated WBC count was appendicitis. The presence of an increased WBC count or left shift carries with it a high sensitivity (79%), and the presence of both high WBC count and left shift has the highest specificity (94%). These values are, therefore, helpful in the diagnosis and exclusion of appendicitis. Although not absolute, the WBC count and left shift can be helpful in the diagnosis and exclusion of appendicitis.
authors.affiliation: Department of Pediatrics, Pediatric Emergency Medicine Unit, Massachusetts General Hospital, Boston, MA 02114, USA. ltwang@partners.org
authors.forename: Linda T
authors.initials: LT
authors.lastname: Wang
authors.forename: Kimball A
authors.initials: KA
authors.lastname: Prentiss
authors.forename: Jill Z
authors.initials: JZ
authors.lastname: Simon
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Doody
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Ryan
mesh_terms: D015746:Abdominal Pain / Q000175:diagnosis / Q000209:etiology; D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D001062:Appendectomy / Q000379:methods; D001064:Appendicitis / Q000175:diagnosis* / Q000601:surgery*; D002648:Child; D002675:Child, Preschool; D004636:Emergency Service, Hospital; D005260:Female; D006801:Humans; D007223:Infant; D007958:Leukocyte Count / Q000706:statistics & numerical data*; D008297:Male; D011237:Predictive Value of Tests; D011336:Probability; D011446:Prospective Studies; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D016896:Treatment Outcome