Evaluation of children with possible appendicitis using technetium 99m leukocyte scan

We evaluated the use of technetium 99m albumin colloid white blood cell (TAC-WBC) scan in 33 children with possible appendicitis. Ten children had appendicitis, four of whom had perforated their appendix at the time of surgery. Children with appendicitis differed from children without appendicitis in the incidence of right lower quadrant rebound tenderness (60% vs 17.4%), and white blood cell count (X10(3)/mm3) (14.0 + 1.9 vs 10.7 +/- 1.0). TAC-WBC scans were interpreted as either positive, negative, or indeterminate for appendiceal pathology. Twenty-five children had positive or negative scans for appendiceal pathology. There were 7 true positives, 2 false positives, 16 true negatives, and 0 false negatives. This resulted in a sensitivity of 100%, a specificity of 89%, an accuracy of 92%, a positive predictive value of 78%, and a negative predictive value of 100%. The TAC-WBC scan was indeterminate (abnormal but nondiagnostic for appendicitis) in eight children (24%), three of whom had appendicitis. The main values of TAC-WBC scan in our study of children with possible appendicitis were that it could be used emergently, it was abnormal in 100% of children with appendicitis, and it had a high negative predictive value (100%). The main limitation of TAC-WBC scan in our study was that it was indeterminate for appendiceal pathology in 24% of children. We recommend that TAC-WBC scan be used in children with possible appendicitis because it may allow outpatient management of up to 48%.