PH and functional class

What is the WHO functional class?

The World Health Organization (WHO) functional class describes how severe a patient’s pulmonary hypertension (PH) is.1 There are four different classes – I is the mildest and IV the most severe form of PH. Assigning a functional class helps the PH healthcare team to understand how the patient is affected by their condition. A goal of PH treatment is to make everyday living easier, so it is very important to have an accurate picture of how PH is affecting a patient’s daily life.

PH WHO functional class

How are patients assigned to a WHO functional class?

To assign a patient to a WHO functional class, the PH healthcare team will ask questions to find out how PH is affecting them.

Why is it important for patients to keep track of their PH symptoms?

The main aim of PH treatment is to improve a patient’s symptoms – ideally to WHO functional class I or II.2 It is helpful for patients to take note of how they are feeling, and write down if they have found something easier or more difficult. This record of symptoms gives the healthcare team more information about how their patient has been getting on since the last clinic visit, and helps them to make decisions about their future treatment.


  1. McGoon M, Gutterman D, Steen V et al. Screening, early detection, and diagnosis of pulmonary arterial hypertension: ACCP evidence-based clinical practice guidelines. Chest 2004;126(1 Suppl):14S–34S.
  2. Galiè N, Hoeper MM, Humbert M et al. Guidelines for the diagnosis and treatment of pulmonary hypertension: the Task Force for the Diagnosis and Treatment of Pulmonary Hypertension of the European Society of Cardiology (ESC) and the European Respiratory Society (ERS), endorsed by the International Society of Heart and Lung Transplantation (ISHLT). Eur Heart J 2009;30:2493–537.

Further information and educational materials can be found in the section PH. It’s personal.

Last updated: February 2, 2015