title: Use of White Blood Cell Count and Polymorphonuclear Leukocyte Differential to Improve the Predictive Value of Ultrasound for Suspected Appendicitis in Children.
abstract: BACKGROUND
  The objective of this study was to examine the use of WBC count and polymorphonuclear leukocyte differential (PMN%) for improving the predictive value of ultrasound (US) in children with suspected appendicitis.
  
  
  METHODS
  We conducted a retrospective cohort study of children undergoing US for suspected appendicitis between January 1, 2010 and December 31, 2012 at a single children's hospital (n=845). Negative (NPV) and positive predictive values (PPV) for appendicitis were calculated for common constellations of US findings and compared with and without the use of laboratory thresholds (WBC>9×10(3)/μL and PMN%>65% for PPV; WBC≤9×10(3)/μL and PMN%≤65% for NPV).
  
  
  RESULTS
  Fifty-one percent of US were considered "equivocal" (ie, appendix incompletely visualized, no primary or secondary signs, or presence of fluid only) and NPV increased significantly for this cohort using laboratory thresholds (41.9% vs 95.8%; p<0.001). Primary signs of appendicitis, without secondary signs, were documented in 18% of examinations, and the PPV associated with this cohort increased from 79.1% to 91.3% (p<0.001) using laboratory thresholds. Secondary signs with or without primary signs were documented in 24% of examinations, and laboratory thresholds improved the PPV in this cohort from 89.1% to 96.8% (p<0.001). Guidelines recommending against the use of CT for very high-risk and low-risk categories (NPV>95% and PPV>95%) on the basis of combined US and laboratory data could have reduced the number of CTs by 27.1% (101 of 373) during the study period.
  
  
  CONCLUSIONS
  The incorporation of WBC count and PMN% can substantially improve the predictive value of US in the diagnosis of suspected appendicitis in children.
authors.affiliation: Department of General Surgery, Boston Children's Hospital, Boston, MA.
authors.forename: Seema P
authors.initials: SP
authors.lastname: Anandalwar
authors.affiliation: Department of Radiology, Boston Children's Hospital, Boston, MA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Callahan
authors.affiliation: Division of Emergency Medicine, Boston Children's Hospital, Boston, MA.
authors.forename: Richard G
authors.initials: RG
authors.lastname: Bachur
authors.affiliation: Department of General Surgery, Boston Children's Hospital, Boston, MA.
authors.forename: Christina
authors.initials: C
authors.lastname: Feng
authors.affiliation: Department of General Surgery, Boston Children's Hospital, Boston, MA.
authors.forename: Feroze
authors.initials: F
authors.lastname: Sidhwa
authors.affiliation: Department of General Surgery, Boston Children's Hospital, Boston, MA.
authors.forename: Mahima
authors.initials: M
authors.lastname: Karki
authors.affiliation: Department of Radiology, Boston Children's Hospital, Boston, MA.
authors.forename: George A
authors.initials: GA
authors.lastname: Taylor
authors.affiliation: Department of General Surgery, Boston Children's Hospital, Boston, MA. Electronic address: shawn.rangel@childrens.harvard.edu.
authors.forename: Shawn J
authors.initials: SJ
authors.lastname: Rangel
mesh_terms: D000293:Adolescent; D001064:Appendicitis / Q000097:blood* / Q000000981:diagnostic imaging*; D015415:Biomarkers / Q000097:blood; D002648:Child; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007958:Leukocyte Count; D008297:Male; D009504:Neutrophils / Q000378:metabolism*; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014463:Ultrasonography
chemical_list: D015415:Biomarkers