Objective: To assess interrater reliability of the New York Heart Association/World Health Organization functional classification as applied by clinicians (defined as both physicians and nurses in this article) to patients with pulmonary arterial hypertension (PAH).
Patients and methods: Between March 16 and August 31, 2007, a survey that described 10 hypothetical patients was completed by physicians and nurses attending a conference on PAH. Results were subsequently validated with physicians and nurses who were contacted online through the Pulmonary Hypertension Association. Respondents were asked to assign each patient's functional class as they would normally in clinical practice.
Results: The functional class evaluations were completed by 113 clinicians, 87 (77%) of whom had participated in PAH trials; 106 (94%) reported using functional class when determining therapy. Clinicians reported a broad range of factors they considered when evaluating functional class, and their assessments of functional class varied widely. The intraclass correlation coefficient was 0.58 for the initial patient survey and 0.62 for the online survey. At best, one patient was ranked as either class II (by 60 clinicians [53%]) or class III (by 53 [47%]). Clinicians' rankings spanned at least 3 functional classes for each of the other patients. Equally divergent rankings were observed among nurses and physicians. Cluster analysis identified clinicians' tendencies toward "higher" or "lower" functional class rankings. Of the 113 clinicians, 101 (89%) thought that the patients described resembled those seen in their practices.
Conclusion: Despite the wide use of the New York Heart Association/World Health Organization functional class in clinical care and as a research tool, interrater agreement may be inadequate. Efforts to promote a uniform approach to evaluating functional class might help to standardize PAH care and research.