The use of tagged white blood cell scans to diagnose appendicitis in pregnant patients

Abstract

A prompt and accurate diagnosis of appendicitis in pregnant patients is important in avoiding premature labor and fetal loss. Computed tomography (CT) scans are accurate, but fetal radiation exposure is high. Ultrasound avoids radiation exposure, but is less accurate as the uterus enlarges. A third option involves the use of technetium-99 tagged white blood cell scans (TWBCS), which have less than 5 per cent of the fetal radiation exposure of CT scans. However, in pregnancy, the value of TWBCS has not been studied. Therefore, a retrospective review of all patients who were pregnant and underwent a nuclear medicine study as part of their evaluation was performed. Thirteen patients were identified from 1999 through 2005. Before receiving a TWBCS, each patient had an indeterminate physical examination and an ultrasound or CT. Patients with negative TWBCS were admitted and observed clinically. There was no relationship between the results of TWBCS and the presence of appendicitis (P = 0.538). The sensitivity of the TWBCS was 50 per cent, whereas the specificity was 73 per cent. TWBCS had a false-positive rate of 27 per cent and a false-negative rate of 50 per cent, and its positive predictive value was 25 per cent. The data suggest that TWBCS in pregnancy is not reliable in evaluating for appendicitis.