A staged physiologic testing approach incorporating inhaled nitric oxide and provocative testing improved diagnostic accuracy for Group 2 pulmonary hypertension by 63.4% compared to standard pressure measurements alone. In this 1,032-participant study, substantial diagnostic discordance persisted across intermediate pulmonary capillary wedge pressure ranges — at 12 mmHg, 25% of patients were misclassified, while at 18 mmHg, 35% remained discordant. Only extreme pressure values below 9 mmHg or above 24 mmHg achieved 90% diagnostic certainty. This diagnostic uncertainty matters profoundly for patient care, as Group 2 pulmonary hypertension represents the most common form of this potentially fatal condition, arising from left heart disease rather than primary lung vessel problems. Accurate classification determines treatment strategy — patients with left heart causes require fundamentally different therapies than those with primary pulmonary arterial hypertension. The staged framework's ability to unmask latent left-sided cardiac limitation through nitric oxide testing could prevent inappropriate treatment with expensive pulmonary vasodilators that may worsen outcomes in left heart disease. However, this preprint awaits peer review, and the complexity of the proposed testing protocol may limit real-world implementation across diverse healthcare settings.