99mTc Anti-CD 15 Monoclonal Antibody (LeuTech) Imaging Improves Diagnostic Accuracy and Clinical Management in Patients With Equivocal Presentation of Appendicitis

Abstract

Appendicitis frequently presents in an atypical fashion leading to misdiagnosis or a delay in diagnosis. This is particularly true in early cases where the patient may be erroneously discharged from an emergency department and will invariably return with perforated appendicitis. The standard of care is hospital admission for observation or early operation. Adjunctive imaging tests have been used with mixed results in this equivocal patient population. The authors studied a promising new monoclonal antibody, 99mTc-labeled anti-CD 15 (LeuTech; Palatin Technologies, Inc., Princeton, NJ), which specifically targets neutrophils and may be used for imaging appendicitis. This prospective, multicenter, open-label study evaluated the diagnostic efficacy and clinical impact of LeuTech scintigraphy for detecting appendicitis in patients with an equivocal presentation. A total of 200 patients (121 females, 79 males; age range 5–86 years; mean age 30.5 ± 16.5 years) completed the study. Management plan was formulated before and reassessed following LeuTech imaging to determine impact on management. Following intravenous injection of LeuTech, the abdomen was imaged with a standard gamma camera for 30 to 90 minutes. Fifty-nine patients had a histopathologic diagnosis of acute appendicitis. LeuTech identified 53 of 59 patients with appendicitis (90% sensitivity) and was negative in 122 of 141 patients without appendicitis (87% specificity). Accuracy, positive predictive value, and negative predictive value were 88%, 74%, and 95%, respectively. Diagnostic efficacy was unchanged in a subgroup of 48 pediatric patients (5–17 years). Diagnostic images for appendicitis were achieved within 8 minutes postinjection in 50% of patients and within 47 minutes in 90% of patients. Significant shifts in patient management decisions were evident following LeuTech results. LeuTech was well tolerated with no serious adverse events reported. LeuTech is a convenient, safe, rapid, and sensitive imaging test for diagnosis of appendicitis and favorably impacts patient management in adult and pediatric patients with equivocal signs and symptoms.