Candidate for the Lee B. Lusted Student Prize Competition
Purpose: Appendicitis is the most common indication for non-obstetric surgery in pregnant women with nearly 10,000 cases of appendicitis during pregnancy occurring annually. Displacement of the abdominal anatomy and the physiological changes of the second and third trimester decrease the accuracy of clinical diagnosis with reported negative appendectomy rates of approximately 40%. Diagnostic laparoscopy, CT, and MRI are the commonly employed strategies to confirm the diagnosis of appendicitis and are assessed here with a cost-effectiveness analysis.
Methods: We developed a decision-analytic Markov model to quantify the health outcomes and costs for the mother and fetus. Pregnant women who were suspected of having appendicitis underwent one of three diagnostic strategies: 1) Diagnostic laparoscopy; 2) MRI scan; 3) CT scan. All women with a positive MRI or CT and all women in the laparoscopy strategy then underwent an appendectomy with the risk of incurring a perioperative complication, including preterm delivery or fetal loss. Finally, due to fetal radiation exposure in the CT strategy, the model included the subsequent health outcomes and costs for children experiencing radiation-associated pediatric cancer. All model inputs were derived from the published literature. The analysis adopted a societal perspective, considering a lifetime horizon, and expressed outcomes in terms of discounted costs, quality adjusted life years (QALY) for the mother and fetus, and incremental cost-effectiveness ratios.
Results: MRI cost $789 per additional QALY gained compared to diagnostic laparoscopy. The MRI strategy cost less and was more effective than CT when the cost of performing an MRI was below $5,395. In a setting where MRI was unavailable, CT cost $1,264 per QALY gained compared to diagnostic laparoscopy. Unless the prevalence of appendicitis was >98% in the screened population, imaging of any type prior to surgery was more cost-effective than diagnostic laparoscopy.
Conclusions: A high level of clinical diagnostic certainty must be reached prior to proceeding to operation without pre-operative imaging in the pregnant patient given the risks of preterm labor and fetal loss associated with operation. Depending on imaging costs and resource availability, both CT and MRI are potentially cost-effective strategies, with the risk of radiation-induced childhood cancer from CT having little impact on population-level outcomes.