Standard Diagnostic Tests Help Identify Appendicitis

A new study suggests that white blood count (WBC) and polymorphonuclear leukocyte differential (PMN%) can improve the predictive value of ultrasound (US) in children with suspected appendicitis.

Researchers at Boston Children’s Hospital (MA, USA) conducted a retrospective cohort study of 845 children who underwent an US examination for suspected appendicitis between January 1, 2010, and December 31, 2012. They then calculated negative and positive predictive values (NPV, PPV) for appendicitis for common constellations of US findings, and compared the results with and without the use of diagnostic WBC and PMN% laboratory thresholds.

The results showed that the ability to differentiate between children with and without appendicitis was significantly improved when the US and laboratory findings were paired. The risk of appendicitis rose from 79.1% to 91.3% when laboratory studies indicated a bacterial infection and sonography showed primary signs of appendicitis, such as increased blood flow or a thickening in the wall of the appendix. The risk of appendicitis rose from 89.1% to 96.8% when laboratory results were abnormal and the US showed secondary signs of appendicitis, such as fat near the appendix.

The ability to single out children who did not have appendicitis was also substantially improved; in children where the US finding showed neither a normal appendix nor evidence of appendicitis, the percentage of children who did not actually have appendicitis rose from 46% to 98.2%, affirming that the laboratory studies were within normal ranges. The study was published early online on January 30, 2105, in the Journal of the American College of Surgeons (JACS).

“We are not advocating that other hospitals adopt our sonographic categories or laboratory value cut-offs for WBC and PMN values, but rather to work collaboratively with their radiologists and emergency room physicians to develop their own approach for categorizing sonographic findings in their patients with suspected appendicitis, and then develop risk profiles that are tailor-made for their patients after incorporation of their institution’s laboratory data,” concluded lead author Shawn Rangel, MD, of the department of surgery.

PMNs are a type of WBC that arises from the myeloid cell line in the bone marrow and help the body to fight infection. PMNs include neutrophils, basophils, and eosinophils, all of which circulate in the bloodstream, as well as mast cells, which reside in soft tissues. Their primary role is to digest any foreign invaders. When PMNs are stained for examination, the cytoplasm takes on a grainy appearance under the microscope, hence they are also known as granulocytes.

Related Links:
Boston Children’s Hospital