title: Lymphocyte Count at 4 Days Postoperatively and CRP Level at 7 Days Postoperatively: Reliable and Useful Markers for Surgical Site Infection Following Instrumented Spinal Fusion.
abstract: METHODS
  A case-control study.
  
  
  OBJECTIVE
  The objective of this study is to identify biochemical markers for surgical site infection (SSI) in posterior instrumented spinal fusion that are not affected by operative circumstances and to determine diagnostic cutoffs for these markers.
  
  
  BACKGROUND
  Numerous biochemical markers may be used for early detection of SSI; however, these markers may be affected by operative factors.
  
  
  METHODS
  We reviewed data on C-reactive protein level and total white blood cell count and differential count before instrumented spinal fusion and at 1, 4, and 7 days postoperatively. The 141 patients in our sample were divided into an SSI group (patients who developed deep SSI) and a no-SSI group. We determined which markers differed significantly between groups and identified those not affected by operative circumstances (operating time, intraoperative blood loss, number of fusion segments) in the no-SSI group. Then, we determined diagnostic cutoffs for these unaffected markers by using receiver-operating characteristic curves.
  
  
  RESULTS
  Three markers were selected: lymphocyte count at 4 days postoperatively (cutoff 1180/μL, sensitivity 90.9%, specificity 65.4%, area under the curve [AUC] 0.80), lymphocyte count of at 7 days postoperatively (cutoff <1090/μL, sensitivity 63.6%, specificity 78.5%, AUC 0.77), and C-reactive protein level at 7 days postoperatively (cutoff >4.4 mg/dL, sensitivity 90.9%, specificity 89.2%, AUC 0.95).
  
  
  CONCLUSIONS
  Lymphocyte count at 4 and 7 days postoperatively and C-reactive protein level at 7 days postoperatively are reliable markers for SSI following instrumented spinal fusion. Lymphocyte count at 4 days should be useful for screening because of its high sensitivity and because it can be measured early. C-reactive protein level at 7 days should be useful for definitive diagnosis given its high sensitivity and specificity and large AUC.
  
  
  METHODS
  4.
authors.affiliation: Department of Orthopedic Surgery, Nara Medical University, Nara, Japan.
authors.forename: Eiichiro
authors.initials: E
authors.lastname: Iwata
authors.affiliation: Department of Orthopedic Surgery, Nara Medical University, Nara, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Shigematsu
authors.affiliation: Department of Spine and Spinal Cord Surgery Center, Nara Prefecture General Medical Center, Nara, Japan.
authors.forename: Munehisa
authors.initials: M
authors.lastname: Koizumi
authors.affiliation: Department of Orthopedic Surgery, Otemae Hospital, Osaka, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nakajima
authors.affiliation: Department of Orthopedic Surgery, Nara Medical University, Nara, Japan.
authors.forename: Akinori
authors.initials: A
authors.lastname: Okuda
authors.affiliation: Department of Orthopedic Surgery, Nara Medical University, Nara, Japan.
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Morimoto
authors.affiliation: Department of Orthopedic Surgery, Nara Medical University, Nara, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Masuda
authors.affiliation: Department of Orthopedic Surgery, Otemae Hospital, Osaka, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Yamamoto
authors.affiliation: Department of Orthopedic Surgery, Nara Medical University, Nara, Japan.
authors.forename: Yasuhito
authors.initials: Y
authors.lastname: Tanaka
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D001799:Blood Sedimentation; D002097:C-Reactive Protein / Q000032:analysis; D016022:Case-Control Studies; D042241:Early Diagnosis; D005260:Female; D006801:Humans; D018655:Lymphocyte Count; D008297:Male; D008875:Middle Aged; D011184:Postoperative Period; D012372:ROC Curve; D013123:Spinal Fusion / Q000009:adverse effects; D013530:Surgical Wound Infection / Q000175:diagnosis / Q000209:etiology*
chemical_list: D015415:Biomarkers; D002097:C-Reactive Protein