Objective:

To evaluate the diagnostic performance of perfusion-only Q-SPECT in patients with suspected CTEPH and develop a method to optimize referral decisions based on Q-SPECT results.

Key Findings:

• Perfusion-only Q-SPECT provides a reliable rule-out tool for CTEPH with a high negative predictive value, particularly beneficial in low-resource settings.
• The absence of perfusion defects is strongly associated with excluding CTEPH, highlighting its diagnostic utility.
• Q-SPECT can significantly reduce unnecessary referrals to specialized centers in low-resource environments.

Interpretation:

Perfusion-only Q-SPECT is a feasible diagnostic alternative in low-resource settings, allowing for effective patient stratification and minimizing delays in diagnosis.

Limitations:

• Perfusion defects may arise from conditions other than chronic thromboembolic disease, potentially reducing positive predictive value and complicating diagnosis.
• The study was limited to a small patient population and a single center, which may affect the generalizability of the findings.

Conclusion:

Perfusion-only Q-SPECT can optimize referral decisions for suspected CTEPH, ensuring timely diagnosis and treatment while reducing unnecessary referrals.