Validity of lung perfusion spect scan matched with a chest radiograph in acute pulmonary embolism

Objective: To validate single photon emission computed tomography (SPECT) lung perfusion scan (LPS) matched with a recent chest radiograph against computed tomographic pulmonary angiography (CTPA) used as gold standard, for diagnosis of acute pulmonary embolism (PE). Study Design: Validation study. Place and Duration of Study: Nuclear Medical Centre, Armed Forces Institute of Pathology, Rawalpindi, Pakistan, from 31th May 2011 to 7th December 2012. Patients and Methods: Thirty patients suspected of acute PE with Wells score >= 2, representing intermediate and high PE probability were enrolled, through non-probability, consecutive sampling. LPS scans, acquired after intravenous injection of 175-200 MBq of Tc-99 m macro albumin aggregates, were matched with chest radiographs (instead of ventilation scans) and reported as positive or negative for acute PE. Outcomes were compared against CTPA results, and diagnostic measures were calculated. Results: LPS scan (matched with chest radiograph) was found to have sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) of 93.33%, each Cohen's Kappa coefficient (k) was 0.866. Conclusion: Lung perfusion SPECT scan matched with a recent chest radiograph is a reliable investigation for the diagnosis of acute PE and can suffice as a stand-alone test to guide patient management. (author)