What Does the Four-Strata PAH Risk Assessment Mean?

The four-strata risk assessment is a clinical tool, formalized in the 2022 ESC/ERS guidelines, that helps doctors track idiopathic or heritable pulmonary arterial hypertension (PAH) during follow-up visits ^[1]. If your specialist says you are at “intermediate-low risk,” it means your estimated risk is lower than the two highest categories, but it is not the same as low risk and does not by itself dictate whether your treatment should change ^[2][3].

The primary medical goal of PAH therapy is to reach and maintain low-risk status, but decisions about adjusting your medications are highly individualized ^[4][1].

A Simplified Follow-Up Tool, Not the Whole Picture

The four-strata model used during follow-up visits (often called the COMPERA 2.0 model) is a simplified assessment based on three specific measures ^[2][3]:

• WHO Functional Class: This is a clinical assessment by your doctor (not a lab test) of how much your symptoms limit your daily physical activities.
• 6-Minute Walk Distance (6MWD): A measure of how far you can walk in six minutes. Be aware that this distance can also be affected by your age, musculoskeletal issues, anemia, and whether you use oxygen.
• BNP or NT-proBNP: A blood test that measures proteins released when the heart is under stress. However, these levels can also be influenced by kidney function, age, heart rhythm problems, and obesity.

To find your risk category, your doctor compares each of these three measures to specific guideline thresholds, assigns each result a score, and averages them ^[2][5][6].

Important: This three-variable calculation is only one part of your specialist’s evaluation ^[7]. It does not replace a comprehensive clinical assessment ^[8]. Your care team also looks at your symptom trajectory, fainting episodes (syncope), signs of right-heart failure, echocardiograms, other medical conditions, and sometimes invasive tests like a right-heart catheterization ^[7][5].

The Four Risk Categories Explained

The guidelines classify PAH into four risk strata based on large, population-level registry data. Note: The mortality percentages below are approximate estimates for large groups of patients over one year; they are not individual predictions or a guarantee of what will happen to you ^[4][9].

• Low Risk: This is the primary treatment target when achievable ^[4]. For the population in this group, the estimated one-year mortality is less than 5% ^[4][9]. However, being at low risk does not guarantee permanent stability, so regular monitoring is still required ^[9].
• Intermediate-Low Risk: Your estimated risk is better than the higher categories, but there is still residual risk and measurable strain on your heart and lungs ^[3][2].
• Intermediate-High Risk: Your results indicate more significant strain on your heart and a higher risk of disease progression ^[2][1].
• High Risk: This indicates severe, unstable PAH with an estimated one-year mortality above 20% for the group ^[1]. This typically requires intensive medical intervention ^[4].

What Intermediate-Low Risk Means for Treatment

Because intermediate-low risk is not the optimal treatment target, your care team may discuss options for modifying your therapy ^[10][11]. However, medication escalation is not automatic ^[12][13].

Decisions to add a new medication (such as targeting the prostacyclin pathway) or switch to a different drug depend heavily on your current regimen, side effects, other health conditions, and your personal priorities ^[4][13].

Crucial Safety Warnings

• Never start, stop, or change the dose of your PAH medications without consulting your specialist.
• If you are on a continuous prostacyclin infusion, an interruption of the pump or line can cause rapid, life-threatening deterioration. Always have an emergency plan in place.
• A risk category is a long-term monitoring tool, not a substitute for urgent care. Seek prompt medical attention for rapidly worsening breathlessness, fainting, chest pain, new confusion, or rapidly increasing swelling.