Ventilation/perfusion single-photon emission computed tomography: a service evaluation

Area of Science:

• Radiology
• Nuclear Medicine
• Pulmonary Embolism Diagnosis

Background:

• Ventilation/perfusion (V/Q) single-photon emission computed tomography (SPECT) is crucial for diagnosing pulmonary embolism.
• Assessing the accuracy of V/Q SPECT services, including overcalling and undercalling rates, is essential for patient safety and quality assurance.

Purpose of the Study:

• To determine the positive rate and negative predictive value (NPV) of V/Q SPECT as indicators of overcalling and undercalling, respectively.
• To evaluate the indeterminate rate as a measure of technical quality and reporter confidence.
• To establish benchmarks for V/Q SPECT performance in both nonpregnant and pregnant patient populations.

Main Methods:

• A retrospective analysis of V/Q SPECT studies conducted over 5 years.
• Classification of V/Q SPECT results into positive, negative, and indeterminate categories.
• Identification of false negatives by reviewing outcomes of patients with negative V/Q SPECT within 3 months, enabling NPV calculation.

Main Results:

• In nonpregnant patients, the positive rate was 24%, NPV was 98.7-100%, and indeterminate rate was 3.6%.
• In pregnant patients, the positive rate was 6.8%, NPV was 100%, and indeterminate rate was 2.3%.
• The indeterminate rate was slightly higher than recommended guidelines.

Conclusions:

• The positive rate and NPV in nonpregnant patients align with published literature, suggesting a safe V/Q SPECT service.
• The study provides the first reported positive rate for V/Q SPECT in pregnant patients, offering a valuable standard for other institutions.
• Positive rate and NPV are effective metrics for assessing overcalling and undercalling in V/Q SPECT services.